AU610666B2 - Managing data storage space on large capacity record media - Google Patents

Description

0t o i 00 0D L- -I COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMELETE SECIFCAION 610666 NAME ADDRESS OF APPLICANT: 9 0 0 0 0.

International Business Machines Corporation Armonk New York 10504 United States of America NAME(S) OF INVENTOR(S): John Edwad KULAKOWSKI Rodney Jerome MEANS ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Managing data storage space on large capacity record media The following statement is a full description of this invention, including the best method of performing it known to me/us:ry Field of the Invention The present invention relates to data storage and record media each having an extremely large data storing capacity, particularly apparatus and methods for employing such media in a user data processing or other information handling environment.

Description of the Prior Art Rewritable or erasable media have been used for 00990 years for recording all forms of information-bearing a 0 o signals. In data processing ervironments, such media o* should exhibit low error rates for ensuring data integrity and rapid storage and recovery of data.

0 m Typically, rewritable or erasable media have been of a 00 ,n the magnetic recording type. Such magnetic media has 0 00 taken the form of magnetic tapes, magnetic disks 00 0 o" "(direct access storage devices DASD) and magnetic 000000 09 0 drums. When such disk media are first used in a 0 0 recording environment, each medium has to be initialized for recording,.including formatting. Such formatting, depending upon the environment, may include an extensive surface analysis with the recording of control information in various addressable data storage areas of the record medium. Typically, in large capacity magnetic storage disks, such a control record 'tJ9"87"011 A 1_:t rcir I *I .r *r S

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S4 S is often called a home address record as set forth on pages 73 and 74 of a publication by Bohl, entitled "Introduction To IBM Direct Access Storage Devices", published by Science Research Associates, Inc., copyright 1981. Such initialization and surface analysis results in identification of the location of media defects. Then the locations and extents of such media defects are recorded in the home address area.

This arrangement allows a recorder to skip over the identified defects. Such arrangements, improve the yield of magnetic media and, therefore, greatly reduce the cost.

Another example of magnetic disk initialization is the formatting of the so-called flexible diskettes used on today's personal computers. Such diskettes are often referred to as being "soft sectored". To enable the personal computer to record and read data on and from such diskettes, a format operation by the personal computer does a surface analysis for identifying unrecordable areas on the diskette and for recording control indicia on the diskette for enabling the recording oeprations.

A problem arises for a user or customer of such media when the media data storing capacity becomes extremely large,

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1 such as in the gigabyte range. Then the time required for 2 such soft sectoring and initi(hlization may become oppres- 3 sive. Accordingly, a better solution to the present day 4 soft sectoring and media initialization is desired.

6 The above referred to magnetic disk media can be overwritten 7 without first erasing the previous contents. In some 8 magnetic media, such as many magnetic tapes, such overwrit- 9 ing was usually preceded by an erasing step. In the magnet- ~~f)ic tape situation, where erasure is first provided, the procedure of so-called "updating data records in place" is J2 not permitted. As a result, magnetic tape was usually written from the beginning of the tape to the end of the J4 tape in one pass for the above stated reason and other operating parameters beyond the scope of the present de- 6, *A scription.

optical recording media has almost an order of magnitude greater data capacity for a given sized recording area than 0 the current day magnetic recording media. Many current day 21 optical media are hard sectored, the sector marks are 22 molded into the media before shipment from a media factory.

23 Such molding occupies media space which could be used for 24 data storage. Also such media to date has been write once/read many (WORM), On the other hand, magnatooptic 26 media is rewritable but currently requires that the previous 27 recordings be erased before new data is recorded in any 28 given data storing area. Therefore, to update a data reco~rd 29 recorded on a inagnetooptic medium requires a first scan of the record area for erasing the proviously recorded data, a TU987011 -3- 1 2 3 4 6 7 8 9 0 0 'p 0 00 00a- *0 0 00 0 14 0 *0 000 a e 0 0 0 00 00618 0 0 00 21 22 23 24 second scan over the record area to record the updated version of the data and when write or record verification is required or desired a third scan fo~r reading the just recorded updated data. For magnetooptic disk media, a complete rotation of the disk is required between the erase scan and the write scan resulting in a relatively low performance magnetooptic recorder. While a separate erase head and a separate write head could be provided on two different actuators, the attendant cost could make magnetooptic recorders noncompetitive. Accordingly, it is desired to provIde better control procedures for using magnetooptic media in information-bearing signal recorders. Such erasebefore-record requirements also presently exist in the so-called phase-change optical disks wherein the recording is represented by the material phases of amorphous and crystalline states.

optical media, including magnetooptic and phase change, are currently subject to many media defects. Since the recording density per unit area is much higher, the sensitivity of the recording to small defects becomes pronounced. Accordingly, such optical media even though being of a high quality, exhibits a high error rate because of the small areas of the media surface employed for recording information-bearing signals.

when such media are employed for use in a data processing environment, a most efficient use of the media is provided by the so-called "count key data" format as describe~d in Bohi supra, on page 27 and pagen 73-75. Another format TU987011-4 -4- 27 1 2 3 4 7 8 9

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00 00 0 00 0 0 a001 0 T0 4 0 0 0 00 "016 0 0 17 00 0 4 g 0 on 01'9 21 22 23 24 26 27 28 29 commonly used in recording information-bearing signals is the fixed block architecture format which arbitrarily divides the disk surface into addressable areas containing a fixed number of recorded signals such as 2K, 4K bytes per addressable area. Such formatting requires identification of all of the fixed bytes areas. The fixed block architecture is referred to and described on pages 27-28, 82-84 and 125 and 126 of the Bohl book supra. Such fixed block architecture is often found on lower performing data processing environments, such as in the personal computer environment.

A significant difference between the CKD and the fixed block architecture is that the CKD format uses only an index mark for each of the record tracks on a disk plus a home address area and count fields as referred to above. The record size is variable such that the data records are recorded as units of contiguous signals not dissected and distributed into a group of fixed block-size sectors. Further, when recording a large number of small records in CXD, a relatively large number of control signals are associated with such small records; still all of the data storagje space can be used for the data and the control records rather than leaving unrecorded areas as found in fixed block architecture. Accordingly, means are desired for effectively using the CKD format on optical disks in an efficient and low cost manner.

Such efficient use may require the interactivity between a control unit and a recorder and in some circumstances, interactive operation between a host, processor, a control unit and a recorder.

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t rrrrr I nclmr~ -6- SlLmary of thQ Invention 0 a aO *000 0 00 o 0 0 Sa *o a 0 0 0 00 a 00 00 0 6 BaO a O 0 0 According to the present invention there is provided in a record medium for storing data, the medium having a large multiplicity of addressable rewritable data storage arce the improvement including, in combination: a volume table of contents (VTOC) recorded on the medium for indicating the data contents of the medium; first indicia in VTOC for indicating allocated ones of the addressable data storage areas; second indicia in VTOC for indicating unallocated ones of the addressable data storage areas that are erased; third indicia in VTOC for indicating unallocated ones of the addressable data storage areas that are not yet erased; and 15 fourth indicia in VTOC indicating unformatted ones of the addressable data storage areas that cannot receive data for storage until predetermined format signals are recorded therein, whereby the record medium is useable for recording and reading operations without requiring the entire medium to be initially formatted.

20 The invention also provides a method of managing data storage space on a record disk comprising the steps of: receiving a record disk having a multiplicity of concentric record tracks, each track having a readable index indicia and indications of the circular extent of the track; 25 initialising the record disk for data recording by the steps of: a) surface analysing a radially outward set of a predetermined number of said tracks, said predetermined number being substantially less than the total number of tracks on the record disk, indicating the location and extent of each detected surface defect; b) recording In each of the surface analysed tracks, indications of the rotational positions of surface defects in the respective surface analysed track; and

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0101,0Lq<04LOAMIOsU 6a c) recording a volume table of contents in a radially outermost one of the said record tracks in said outward set to contain the address of the tracks in the outward set as being free tracks available to be allocated for data storage and an indication that all of said tracks other than said outward set are not available for data storage until formatted.

The invention also provides in a data storage subsystem having a control unit including program means for operating the control unit and the subsystem, a disk recorder operatively coupled to the control unit and having a large capacity disk recording surface; the improvement including, in combination: operating program means including a program dispatcher in said control unit for effecting subsystem operation which includes recording data onto the large 0 0 capacity disk surface and reading data recorded on the disk surface; P, o' 15 formatting program means in the control unit, including surface analysis o0 o o controlling program means and home address recording program means which records locations of defects in a respective track in a home address record in such track; *o said dispatcher having initialisation programming means operative to cause the control unit to check the large capacity disk surface to determine whether or not the 20 disk surface has been initialised, and if not initialised, operative to activate the 6 o formatting program means a given plurality of times for surface analysing and o00 0 formatting a predetermined number of record tracks at a predetermined radial portion 00 0 0° thereof and recording a volume table of contents (VTOC) in a predetermined one of said predetermined set of tracks; 0 ,n 25 the dispatcher having further intermediate format 'initiating program means activated when the large capacity disk surface is not currently being used for recording or supplying readback signals from and to the control unit for activating said formatting program means to format a second predetermined number of said unformatted record tracks, beginning with a radially outwardmost one of 'he unformatted record tracks; and said dispatcher cycling through all of its operations such that said intermediate i 91~rOItrg3~aE&5Z)Ie 6b formatted program means is activated as a lower priority one of operations to be performed in the subsystem.

The invention also provides in a machine-sensible and recordable record medium of the rotatable disk type for storing data, the medium having a large multiplicity of addressable data storage tracks which are concentrically arranged on the rotatable medium; the improvement including, in combination: a volume table of contents (VTOC) recorded on the record medium in a one of said record tracks for indicating the data content and the current status of the record tracks on the medium; first machine-sensible indicating data stored in said VTOC for indicating allocated ones of the addressable data storage tracks; econd machine-sensible indicating data stored in said VTOC for indicating 15 unallocated ones of the addressable data storing tracks; and fourth machine-sensible indicating data stored in said VTOC for indicating unformatted ones of the addressable data storing tracks that cannot receive data for storage until predetermined format signals are recorded therein such that the record medium is useable for machine sensing and recording operations without initially ot*oe 20 formatting the entire record member.

4900 4 a4 The invention also provides a data storage system for storing and retrieving data with 0 40 S" respect to a record medium which has a multiplicity of addressable rewritable data storage areas which are initially presented in an unformatted record member entity, 25 the system including means for formatting portions of the medium and for reading and writing data in formatted storage areas under the control of a local or remote processor, means to maintain a volume table of contents (VTOC) recorded on the medium for indicating the status and the data contents of the medium, including means to indicate which storage areas are allocated ones of the addressable data stor' g areas; t means to indicate 'hieh storage areas are unallocated ones of the addressable r II. i 6c data storage areas that are still storing data; and means to indicate which potential storage areas are unformatted ones of the addressable data storage areas that cannot receive data for storage until predetermined format signals are recorded therein and means by reference to the VTOC to progressively format the record medium between accesses to the data storage areas.

The invention also provides a record storage member having a multiplicity of addressable record storage areas each of which is subject to defects, the improvement including, in combination: first machine-sensible control indicia on the storage member for indicating which of the addressable record storage areas have been initialised for identifying the 0 °existence of said defects within the respective addressable record storage areas; second machine-sensible control indicia on the storage member for indicating 0. 0, which of the addressable record storage areas have not yet been initialised; and 15 third machine-sensible control indicia on the storage member for indicating which of said initialised addressable record storage areas have been allocated for information-handling operations.

The invention also provides in a machine-effected method of using a storage member :o 20 having a recording surface subject to defects and capable of having a maximal number of addressable data storage areas, including the machine-executed steps of: S0 accessing a storage member which has no addressable data storage areas initialised for data recording; initialising, including surface analysing, a predetermined number of the 25 addressable data storage areas for any ensuing data recording, said predetermined number being less than the number of the addressable data storage areas; conducting data processing operations with respect to the storage member which Include recording data into the Initialised addressable data storage areas; and when the storage member is not participating in said data processing operations, initialising, including surface analysing, additional ones of said addressable 6d data storage areas until the storage medium has said maximum number of initialised addressable data storage areas.

Preferably, the record medium having a multiplicity of addressable record tracks is received unformatted and not surface analysed (unprocessed, herein termed "new") in a user environment. Each of the new record tracks has an index for indicating its beginning point. In the user environment, a first initialisation of the record medium for signal recording includes the steps of surface analysing a selected subset consisting of a predetermined number of said new record tracks with the predetermined number being substantially less than the total number of tracks on the record medium. The detected surface defects are indicated and identified by location and extent. The 1** 0 surface analysed tracks are then formatted, In such formatting, the indication is ooB recorded in a so-called home address area of each of the surface analysed tracks S* which includes recording indications of the track positions and extent of the surface defects. Such formatted record tracks can now receive and store data.

ao: Preferably, a volume table of contents (VTOC) recorded in one or more of said record tracks includes identification of which tracks of the disk are in the surface analysed and formatted sets; which tracks are yet unformatted and not surface analysed. When 20 a record medium is hard sectored, the individual addressable sectors can be demarked I o c, with alternate sectors being assigned to receive the data.

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1 t 4? 2 V 1 As the record medium is used, the VTOC is updated for 2 indicating which of the tracks in the set are allocated for 3 data storage and which are free and available for alloca- 4 tion. When the record medium is not being used for recording signals thereon or reading signals therefrom, additional 6 ones of the new tracks are surface analyzed "in-line" and 7 identified in VTOC as being available for formatting. Once 8 formatted, such tracks are available for data recording.

9 This in-line surface analysis and formatting is repeated until all of the record tracks in the record medium have o1 been surface analyzed and formatted. The term "in-line" ,l means that media formatting and surface analysis is automatt ically interleaved between day-to-day data processing 'U operations.

I G When a record medium requires erasure of previously recorded I .17 data before new data is recorded, the VTOC includes indicao °1 tiono of which tracks are unallocated and have been erased, ready to receive data, and which tracks are unallocato no2 ed but not yet erased. When the record medium is not being 21 uoosed for recording data or for reading data, then the 22 unallocated, not-yet-eranosed tracks are erased "in-line" for 23 making them more readily available for data recording. Xn a 24 spocific aspect of the invention, whenever theo record medium has used but unallocatod tracks that are not yet erased, all 26 erasure procedures are completed before additional ones of 27 the new record tracks are surface analyzed and then format- 28 ted.

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TUO987011 1 A host processor employing the record medium for data 2 storage can determine that a sequential data set is being 3 recorded and that the recording can be applied to any of the 4 unallocated and erased record tracks rather than to the record tracks previously storing such a sequential data set.

6 This procedure eliminates the erasure step to be interleaved 7 between the request for recording and the actual recording.

8 9 The foregoing and other objects, features, and advantages of 0 the invention will be apparent from the following more i particular description of preferred embodiments of the 2 invention, as illustrated in the accompanying drawings.

14 Description of the Drawing .1116 Fig. I diagrammatically illustrates a record medium using 8 *4 41 7 the present invention.

o Fig. 2 is a block diagram showing a recorder of the magnetooptic type which employs the Fig. 1-illustrated record 21 medium.

22 23 Fig. 3 is a simplified block diagram of a host processor and 24 control unit connected to the Fig. 2-illustrated recorder.

26 Fig. 4 iS a maehino operations chart of a host processor 27 connected to the control unit of Fig. 3 showing those space 28 management, machine operations used to employ the present 29 invention.

TU98O7011181 -48- Fig. 5 Is a simplified machine operations chart for the host processor for enabling certain recording operations.

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2 4 a *.a 22 23 24 26 2.7 28 29 Referring now more particularly to the drawing, like numerals indicate like parts and structural features in the various figures. As usual, magnetooptic disk 30 has a volume table of contents (VTOC) 10 recorded in the radiallyoutermost track of the disk. The addresses of the concentric tracks (not shown) in data area 13 on disk 30 begin with the lowest address track as the radially-outwardmost track and increasing addresses to the radially-inwardmost track. Disk 30 has a single radially-extending index line 11 which signifies the beginning of the recording area for each of the record tracks of disk 30. In the initial area of each record track is a home address area HA 12. Such record tracks can be concentric separate tracks, convolutions of a single spiral track, logical tracks superposed on other physical indicia, etc.

VTOC 10, in accordance with the present invention, includes four recorded areas identified space utilization of recording area 13. It is to be appreciated that VTOC 10 includes other information than that described for practicing the preonnt invention. Xn a first VTOC area 14, all of the record tracks of disk 30 that are currently allocated for storing information-boaring or data signals are identified.

Such identification can be by the physical address reterred to above, can be a directory which allows indirect TU987011 I addressing from a logical address base to the physical 2 address base or other form of indication. A second VTOC 3 area 15 identifies the physical addresses of the free and 4 erased record tracks of disk 30. Such free and erased record tracks are unallocated for data storage but have been 6 erased, as will b~ecome apparent, and therefore, are ready to 7 receive data signals for recording. A third VTOC section 16 8 identifies the free (unallocated) tracks that are not yet 9 erased. Such free tracks are identified by the physical aoaddresses are those that were previously recorded into and Shave been deallocated Crom storing data. Therefore the '12 free, not erased tracks are available for allocation but are 4::'j3 not yet ready to receive recorded information in those disks 0 30 that require erasure of rreviously-recorded data before new data can be recorded. When a disk 30 has the capability 0004' of overwriting recorded data, then the third VTOC section 16 17 may be dispensed with. A fourth VTQC area 17 identifies the "661 radially-outwardmost ones of the new non-analyzed plus the 0 of 0001 surface-analyzed but unformatted recor. tracks. The formatted record tracks have a H-A record recorded therein (as 21 later described) whereas the unformatted tracks have been 22 surface analyzed but have no home address record recorded 23 therein. The new tracks have not yet been surface analyzed.

24 In a preferred embodiment of the invention, the shaded area 26 of HA 12 represents a radially outward and abbreviated-set 27 of record tracks initially formatted for receiving data 28 signals for storage; thence indicated in first VTOC section 29 14. The fourth VTOC area 17 identifies the radial track of disk 30 which is a next radially inward track that han not TUh987011 2 3 4 7 8 9 1 11 f6 ~18 21 22 23 29 been surface analyzed plus the radially-outermost track that was surface analyzed but not yet formatted.

The space management of disk 30 can be porformed in a host processor attaching a data storaje system having a laterdescribed programmable control unit. Such programmed space management needs information stored in VTOC 10 for the space management functions. The space management functions may be performed in the programmable control unit instead of a host processor. In either event, the machine operations perform the same functions as later set forth. The term "space management" means either a host processor or control unit executing computer programs for performing the machine operations shown in Figs. 4 and 5. As shown in Fig. 3, the host processor has the space management.

For improving performance, a portion of VTOC 10 is inserted into later-described program space status table (SST) SST 20 is created from VTOC 10 each time the recorder is powered on, reset, etc. SST 20 has four portions corresponding to the four VTOC areas 14-17. "Allocated" field 21 of SST 20 contains a subset of VTQC area 14. The SST stored "allocated" information can be the total number of allocated tracks of disk 30, and identification of a predetermined set of the last referenced ones of the allocatod set of tracks. For example, up to fifty of the allocated tracks can be identified in field 21. Similarly, the free and erased tracks identilied, in second VTOC portion 15 have some of their addresses recorded in field 22 of SST 20. For example, the twoenty radially-outwardmost ones of the free TUJ987011-1 _11- 1 and erased tracks may be identified in SST 20. In an 2 3 4 6 7 8 9 10 09@Q*S o 9 .44* 0.4 *10 o17 0 60 9 20 o 99 0 *0 22 23 24 26 27 28 alternate arrangement, the free and erased tracks that have an address affinity to the allocated tracks identified in field 21 can be listed in field 22. Such affinity is the radial proximity of the free and erased tracks to the allocated tracks last referenced. A third SST 20 field 23 identifies the free but not erased tracks. Such free but not erased tracks are preferably a radially-outwardmost set of the free and erased tracks for enabling a quick examination of which tracks can be next erased. Also the total number of free and erased tracks and the free but not erased tracks are respectively stored in fields 22 and 23. Such numbers can also be used for analysis of the disk 30 usage.

Finally, in SST 20, field 24 contains the physical addresses of the radially-outwardmost one of the raw, not surfaceanalyzed and unformatted tracks of disk 30. Such information may be used for load balancing and other purposes as may be devised in a data processing environment.

An optical recorder with which the present invention may be advantageously employed is shown in Fig. 2. A magnetoo.tic record disk 30 is mounted for rotation on spindle 31 by motor 32. Optical head-carrying arm 33 on head arm carriage, generally denoted by numeral 34, moves radially of disk 30. A frame 35 of the recordor suitably mounts carriage 34 for reciprocating radial motions. The radial motions of carriage 34 enable access to anyone of a plurality of concentric tracks or circumvolutions of a spiral track for recording and recovering data on and from the disk.

Linear actuator 36 suitably mounted on frame 35, radially TU987011 12- 1 moves carriage 34 for enabling the track accessing. The 2 recorder is suitably attached to one or more host processors 3 37, such host processors may be control units, personal.

4 computers, large system computers, communication system.s, image process processors, and the like. Attaching circuits 6 38 provide the logical and electrical connections between 7 the optical recorder and the attaching host processors 37.

8 9 Microprocessor 40 controls the recorder including the attachment to the host processor 37. Control data, status .~11 data, commands and the like are exchanged between attaching 4,12 circuits 38 and microprocessor 40 via bidirectional bus 43.

Included in microprocessor 40 is a program or microcode #114 storing, read-only memory (ROM) 41 and a data and control signal storing random access memory (RAN) 42.

17 The optics of the recorder include an objective or focussing *0 o 6$8 lens 45 mounted for focussing and tracking motions on head 0 19 arm 33 by fine actuator 46. This actuator includes mechanisms for moving lens 45 toward and away from disk 30 for 21 focussing and track following and seeking movements radially 22 of disk 30; for example, for changing tracks within a range 23 of 100 tracks so that carriage 34 need not be actuated each 24 time a track adjacent to a traok currently being accessed is to be accessed. Numeral 47 denotes the two-way light path 26 between lens 45 and disk 27 28 In magnetooptic recording, magnet 40 provides a weak mag- 29 netic steering field for directing the remnant magnetization direction of a small spot on disk 30 illuminated by laser PTU987011 13 -13- ~~2 1 2 3 4 6 7 8 9 11 0 0* *a a 1 2 23a 2,9~ 3 0 light from lens 45. T he laser light spot heats the illuminate spot on the record disk to a temperature above the Curie point of the magnetooptic layer (not shown, hut can be an alloy of rare earth and transitional metals as taught by Chaudhari et al., US patent 3,949,387). This heating enables magnet 48 to direct the remnant magnetization to a desired direction of magnetization as the spot cools below the Curie point temperature. Magnet 48 is shown as oriented in the "write" direction, binary ones are recorded on disk 30 normally are "north pole remnant magnetization". To erase disk 30, magnet 48 rotates so the south pole is adjacent disk 30. Magnet 48 control 49 which is mechanically coupled to rotatable magnet 48 as indicated by dashed line 50, controls the write and erase directions. Microprocessor 40 supplies control signals over line 51 to control 49 for effecting reversal of the recording direction.

it is necessary to control the radial position of the beam following path 47 such that a track or circumvolution Is faithfully followed and that a desired track or circumvolution is quickly and precisely accessed. To this end, focus and tracking circuits 54 control both the coarse actuator 36 and fine actuator 46. The positioning of carriage 34 by actuator 36 is precisely controlled by control signals supplied by circuits 54 over line 55 to actuator 36.

Additionailly, the actuator control by circuits 54 is exercised by control signals travelling over lines 57 and 58 respectivoly for focus and fine tracking and switching actions of fine actuator 46. Va~ious servo positioning controls may be successfully employed.

TU987011 -14- 1 2 3 4 6 7 8 9 Ai 9 The focus and tracking position sensing is achieved by analyzing laser light reflected from disk 30 over path 47, thence through lens 45, through one-half mirror 60 and to be reflected by half-mirror 61 to a so-called "quad detector" 62. The symbol 62 also includes optics, such as a hemicylinder lens, for processing a light beam before the beam impinges on the detector surfaces. Quad detector 62 has four photo elements which respectively supply signals on four lines collectively denominated by numeral 63 to focus and tracking circuits 54. Aligning one axis of the detector 62 with a track center line, track following operations are enabled. Focussing operations are achieved by comparing the light intensities detected by the four photo elements in the quad detector 62. Focus and tracking circuits 54 analyze the signals on lines 63 to control both focus and tracking.

Recording or writing data onto disk 30 is next described.

it is assumed that magnet 48 is rotated to the desired position for recording data. Microprocessor 40 supplies a control signal over line 65 to laser control 66 for indicating that a recording operation is to ensue. This means that laser 67 is energized by control 66 to emit a highintensity, laser light beam for recording; in contrast, for reading, laser 67 emits a reduced-intensity beam that does not heat the illuminated spot on disk 30 above the Curie point. Control 66 supplies its control signal over line 68 to laser 67 and receives a feedback signal over line 69 indicating the laser 67 emitted light intensity. Control 68 adjusts the light intensity to the desired value. Laser 67, a somiconduc.or laser such as a gallium arsenide diode TUJ9B70 11 1 2 3 4 6 7 8 9 a0 94 690 0 014 4 0 2 0 18 0 laser, can be modulated by data signals so the emitted light beam represents the data to be recorded by such intensity modulation. In this regard, data circuits 75 (later described) supply data indicating signals over line 78 to laser 67 for effecting such modulation. This modulated light beam passes through polarizer 70 (linearly polarizing the beam), thence through collimating lens 71 toward half mirror 60 in light path 72 for being reflected toward disk 30 through lens 45. Data circuits 75 are prepared for recording the microprocessor 40 supplied suitable control signals over line 76. Microprocessor 40 in preparing circuits 75 is responding to commands for recording received from a host processor 37 via attaching circuits 38. Once data circuits 75 are prepared, data is transferred directly between host processor 37 data circuits 75 through attaching circuits 38. Data circuits 75 also has ancillary circuits (not shown) relating to disk 30 ancillary or format signals, error detection and correction signals and the like.

Circuits 75, during a read or recovery action, strip the ancillary signals from the readback signals before supplying corrected data signals over bus 77 to host proocessor 37 via attachment 38.

Reading or recovering data from~ disk 30 for transmission to a host processor requiires optical and electrical processing of the laser light beam from the disk 30. That portion of the reflected light (which has its linear polarization from polarizer 70 rotated by disk 30 recording using the Karr affect) travels along the two-way light path 47, through lens 45 and hal ~-tirrors 60 and 61 ho, the data detection TV 987011 -6 _16- :1 2 3 4 6 7 8 9 4 b P 18 "°22 2 3 o4124 "26 27 24 o 20 29 portion 79 of the head arm 33 optics. Half-mirror or beam splitter 80 divides the reflected beam into two equal intensity beams both having the same reflected rotated linear polarization. The half-mirror 80 reflected light travels through a first polarizer 81 which is set to pass only that reflected light which was rotated when the remnant magnetization on disk 30 spot being accessed has a "north" or binary one indication. This passed light impinges on photo cell 82 for supplying a suitable indicating signal to differential amplifier 85. When the reflected light was rotated by a "south" or erased pole direction remnant magnetization, then polarizer 81 passes no or very little light resulting in no active signal being supplied by photocell 82. The opposite operation occurs by polarizer 83 which passes only "south" rotated laser light beam to photo cell 84. Photocell 84 supplies its signal indicating its received laser light to the second input of differential amplifier 85. The amplifier 85 supplies the resulting difference signal (data representing) to data circuits for detection. The deharcted signals include not only data that is recorded but also all of the so-called ancillary signals as well. The term "data" as used herein is intended to include any and all information-bearing signals, preferably of the digital or discrete value type.

The rotational position and rotational speed of spindle 31 is sensed by a suitable tachometer or emitter sensor Sensor 90, preferablv of the optical sensinq type that senses dark and light spots on a tachometer wheel (not shown) of spindle 31, supplies the "tach" siqnals (digital TUD87011 -17- 1 2 3 4 6 7 8 9 1 42 4 #4 0'T 22 23 24 26 27 28 29 signals) to RPS circuit 91 which detects the rotatioinal position of spindle 31 and supplies rotational informationbearing signals to microprocessor 40. Microprocessor employs such rotational signals for controlling access to data storing segments on disk 30 as is widely practiced in the magnetic data storing disks. Additionally, the sensor 90 signals also travel to spindle speed control circuits 93 for controlling motor 32 to rotate spindle 31 at a constant rotational speed. Control 93 may include a crystal controlled oscillator for controlling motor 32 speed, as is well known. Microprocessor 40 supplies control signals over line 94 to control 93 in the usual manner.

As seen in Fig. 3, host processor 37 is operatively connected to a programmable control unit 101 by interface 102.

Such interface 102 can be the interface between IBM*constructed host processors and the programmable control units used in connection with such IBM host processors. In addition, dash line 103 indicates special signals supplied by host processor 37 to programmable control unit 101 in connection with space management of ma~notooptic DASD 105.

Such special signals travel over the interface 102 but are separately illustrated in Fig. 3 for more clearly illustrating the invention. Such signals constitute an indication that record areas that contain recorded signals can be freed, moved from the allocated status to the free but not erased status. Further such indications may include that the data being recorded by host processor 37 is of the sequential type. Rather than recording such sequential data over previously recorded tracks, space management 37A can *Registered Trade Mark TU987011 -18- W_-wwH, 7 8 9 4 .'12 is %0

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22 6 0^ %20/ 23 24 26 27 28 29 access from SST 20 the free and erased tracks f,)r allocation to the sequential data to be next received from host processor 37. Such allocation eliminates the need for erasing previously recorded tracks before the recording occurs.

Such time saving helps the efficiency of host processor 37.

Xn a similar manner, control unit 101 controls the operation of magnetooptic DASD 105 as indicated by the interconnection 106. Such controls may be the control used in connection with the apparatus described by Bohl supra. Control unit 101 passes the space management con. 'ol as indicated by dash line 107. As set forth in more detail in Fig. 4, such controls are particularly directed toward VTOC 10 and the surface analysis controls for initializing the disk 30 of magnetooptic DASD 105, Host processor 37 has an internal memory diagrammatically represented by SST 20 which contains the various fields described with respect to Fig. 1 and which are used by space management 37A.

Fig. 4 illustrates in flowchart form tho machine operations effected in the Fig. 3-illustratod apparatus by space management 37A that are pertinent to an understanding of the present invention. The host orocessor 37 executes programs for effecting the machine operations represented in Pig. 4.

One of the programs is dispatcher 110 which coordinates operation of all space manaqement program execution and has a design that is well known in the programming art. Activa-.

tion of space management 37A in in accordance with known programming techniques. Arrows 11 rovprosent, program calls to various programs to be executeod for performing machine TU987011 2 3 4 7 8 9 11 12

C

is 13

:I

24 I t 26 27 28 4 19 20 oa 0 t 22 S23 24 25 26 27 28 29 operations not pertinent to an understanding of tho present invention but which are found in a control unit for a data storage subsystem. As a practical matter, programs for implementing machine operations not pertinent to an understanding of the present invention would most likely be a greater proportion of programs executed by host processor 37. Dispatcher 110 sets a priority of execution of the various programs. A low level priority of the programs is assigned to implement one portion of the invention when the magnetooptic DASD 105 is not recording data on disk 30 nor reading data from disk 30 not reserved or allocated).

Logic path 112 represents the entry into such space management machine operations. The first machine operation indicated by numeral 113 (free NE) examines SST 20 field 23 for determining whether or not there are any tracks of disk that had been deallocated but not yet erased (free but not erased NE). Assuming there are some free NE tracks, SST 20 has a nonzero value in field 23. Space management 37A identifies a one of such tracks which may have a physical address stored in field 23 or may require access to VTOC third portion 16 for identifying one roee NE track.

Control unit 101 then actuates tho magnotooptic DASD 105 to move fine actuator 46 to the addressed track. Then control unit 101, in rosponse to space managomont 37A, commands magnetooptic DASD 105 to erase that track an indicated at stop 114. Upon successful completion of the track orasure, which uses normal data reording tochniquns, space managemont 37A at step 115 moves the identification of the justerased track from the third VTOC portion 16 to ftheo oecond VTOC portion 15 and updaotes SST 20 by indicating in field 22

T

U987011 16 o o 4 o 4 a 23 2S 26 27 28 that the just-erased track is now ready to receive data to be recorded; the identification of any such track is deleted from the free NE field 23. At a minimum, the number of free tracks but not erased indicated in numeral 23 are reduced by one where the number of free and the number of erased tracks indicated in field 22 is increased by one. Similar counts are also stored in VTOC 10. Upon completion of machine operations step 115, the dispatcher 110 becomes active.

Under certain circumstances, the erasure of the track in step 114 may be a free-standing operation, control unit 101 may be disconnected during erasure from magnetooptic DASD and, therefore, may return to a dispatcher 110 leaving an electronic note to itself to return to the machine operation 115 when the track erasure is completed.

While it is proforred that a single track be erased at a time to enable a maximum number of requested recording and roadback operations, no limitation to a single track erasure is intended.

In one embodiment, when space management finds no free, noterasod tracks at decision stop 113, it then proceeds to decision stop 116 to determine whether or not all of the record tracko of disk 30 have boon formattod. It is to be understood that steps 113 and 116 may bo both indepondently activated fxom dispatcher 110. Space management eamines field 24 of SST .10 for determining whether or not a traek address is recorded therein. If no track address is ro~orded or a track address having a value one greater than tho addrons of the adialy-inwardnost track ot disk 30 is T987011 "S1- 7 7 8 9 11.

:23.

126 2 8 "o°1.8 I Io 29 ~21 3 recorded, then space management has determined that all of the tracks of disk 30 have been formatted. At this point, space management follows program path 117 to return path 109 returning to dispatcher 110.

In the event that field 24 contains a physical address of a new track of disk 30, then one of the new tracks is then surfaced analyzed and formatted in subroutine 120. In machine operations step 121, the track identified in field 24 is the next track to be formatted and is assigned for the formatting operation. in step 122, space management 37A causes control unit 101 and magnetooptic DASD 105 to surface analyze and test the just-identified new track. such surfdce analysis includes detecting and identifying surface defects for later recording in the home address area of the track being surfaced analyzed.

During the surface analysis, either magnotooptic DASD 105 or the control unit 101 collects the identification of the detected surface defects, their circumferential locations and extents. Upon completion of such accumulation of detected defect identifications, space management 37A moves to step 123 wherein the defects are accumulated in table form ready for recording in the home address area in the ensuing step 15. An a part of Step 123, control unit 101 causes magnetooptic DASD 105 to erase the just surfaceanalyted track. Volloving sunh erasure, the home address record A is written in that track in step 12S. Stop 124 TU987011 4 6 7 8 9 11,

S*

16

*B

*ag '.9 23 24 24 26 28 indicates that other data processing may be performed before step 12S effects formatting.

Upon the successful completion of track formatting, field 24 of SST 20 and VTOC 10 are updated by selecting the next higher track address (the address of the next radiallyinwardmost track) for recording respectively in field 24 of SST 20 and in fourth VTOC portion 17. SST 20 and VTOC portion 15 are updated to show availability of each additional formatted track. When the radially inwardmost track is erased, the stored address is for no track, is one greater than the highest addressed track. Upon completion of machine operations step 125, program execution goes back to dispatcher 110.

Dispatcher 110 also activates allocate-deallocate module 128. Allocate-deallocato module 128 may also be ca led by another program module being executed for performinq an allocate request generated in host processor 37. In any evant, allocate-deallocate modulo 128 is constructed and performs operations as found in present day memory control computers which allocate and deallocate addreasablo data storage areas. if allocate module 128 during an allocation procedure being performed finds an unallocated orased addrossable track identified either in SST 20 field 22 or in second VTOC portion 15, the allocation is successful. Such successful allocation, results in indicating "he allocation in comploto over line 129 for enabling the nost processor to command recording in the just allocated data storage area.

Xf the allocate procedure was caused by execution of another TU987011 1 program within host processor 37 sending a request over line 2 127A, then the successful allocation is indicated on line 3 129A to enable that program execution to be continued.

4 All deallocations of tracks by module 128 are successful.

6 Each deallocation includes moving the identification of the 7 record track or tracks being deallocated from the first VTOC 8 portion 14 as an allocated track to third VTOC portion 16 9 and SST 20 which indicates the track is unallocated but not erased. Space management may not know whether or not data 11- in fact had been recorded in the just deallocated track, I, however, for purposes of integrity, it is assumed that some

I

13. data has been recorded in the just deallocated track. All ,of the above-described operations are represented in Fig. 4 5y by numeral 131. Execution of these operations completes the 16 deallocation procedure for enabling dispatcher 110 to select another program for execution.

I8 When an allocation attempt fails because there are no 4 3 04 addressable data storage tracks identified in the second 0421. VTOC portion 15, the numbers of free and erased tracks i 22 indicated in field 2.2 of SST 20 and second VTOC portion 23 are zero, then space management has to be performed at the 24 next available moment for obtaining additional allocataioe data storage space.

26 27 The failed allocate program path 132 loads to decision stp i 28 133 to determine whether or not there are any free NE record 29 tracks identified in third VTOC portion 16 as also indicated by a nonereo number in field 23 of SST 20. Whon SST field T907011 TU9B7011 4-I At t- 2 4 7 8 9

I'

12" 16

IT

r8a 22 23 24 26 27 28 29 23 is nonzero, then execution of the machine operations of Fig. 4 proceeds to erase tracks in step 134 for making those tracks available for allocation. Upon the completion of erasure, the number in field 23 is reduced while the number in field 22 is made nonzero; VTOC 10 is updated to reflect the erasure by moving the indication of the just erased tracks from third VTOC portion 16 to second VTOC portion Following the successful completion of erasure, the justerased tracks then are allocated in step 135 with space management then returning to dispatcher 110.

In the event there are no unallocated NE tracks detected at decision step 133, then some remaining unformatted tracks on disk 30 are processed. At decision step 138 (all FMT), space management examines SST 20 field 24 for determining whether or not there are any remaining unformatted tracks on disk 30. If there are none, all of the tracks on disk have been formatted, then space management follows path 139 to dispatcher 110, there is nothing that can be done to satisfy the allocation request at this time the disk is fully allocated. on the other hand, at decision steap 138, if there are some unformatted tracks indicated by f4ield 24 of SST 20 or fourth VTQC portion 17t then at least one of the unformatted tracks, and if more than one track has been requested, a plurality of such unformathed tracks are formatted at function step 140. Function step 140 includes all oE the steps set forth with respect to formatting in the subroutine 120. It is to be noted that surface analysis of the tracks may be completed yet the a- TUO87011 -7 12- 13, '4 16 o.19 21 21 23 24 26 27 28 29 formatting of the analyzed tracks (step 125) may not have yet been completed. In this later instance, only step 125 of subroutine 120 is performed.

Upon completion of formatting a requisite number of unformatted tracks at step 140, space management proceeds to allocate the just formatted and erased tracks at step 135.

In a practical implementation, the programming used for performing operation step 135 is a part of allocate module 128.

All of the above description relates to erasing and formatting tracks on an in-line basis in which host processor 37 interleaves such erasing operations and formatting operations between recording and readback operations. To initialize disk 30 when first placed on magnetooptic DASD 105 or when disk 30 is a non-removable disk when magnetooptic DASD 105 is first varied on to host processor 37, space management initializes a radial-outwardmost set of record tracks for enabling recording and readback operations to ensue. In an alternative procedure, a factory may perform the initial formatting of the radially-outward tracks in disk 30. In that event, space management does not initialize the disk 30 in a user environment. Initialization may also be instituted by space management causing control unit 101 to sense the disk 30 for VTOC 10; if there is no VTOC 10 indicates an unformatted disk. Then initialization can be started by space manaqemontk In any event, an initialization command in sensed at decision step 154.

TU987011 -26- 1 2 3 4 6 7 8 9 lt 2 27 16 2.7 9 If the initialization command had previously been performed for disk 30, as can be sensed by reading VTOC 10, then no action is taken. For an uninitialized disk 30, space management proceeds from decision step 154 to a series of steps 155-157. At step 156, a surface test or analysis is made of a predetermined number of radially-outwardmost tracks on disk 30. For example, the first 100 radially-outwardmost tracks are surface analyzed as described with respect to the steps 120.

Upon completion of the surface analysis, the tracks are erased and home addresses (HAs) are written on the respective tracks during step 155 including the outermost track which is to receive VTOC 10. Then, at step 157, the VTOC is written in the outermost track. Upon completion of this disk initialization, space management returns to dispatcher 110 for enabling host processor 37 to perform other machine operations via return path.

rig. 5 illustrates machine operations used when nonsequential data is being recorded, those situations wherein host processor 37 desires to maintain the data in the same track that a previous version of the data was stored. It is to be understood that host processor 37 can be 'programmed to allow movement of non-sequential data from track to track on disk 30 f4or avoiding interleaving an erasure step between ai request to write and the actual writing or recording operation on disk 30. In the latter instance, the directory of the data stored on disk 30 in logical, VTOC 10 includes a directory which converts a rTU 907011 a7 -27- MO-2 1 2 3 4 6 7 8 9 12 16 4 21 22 23 29 logical number or address into a physical or track address.

Such logical addressing is found in present day diskettes and hard disks as used with personal computers. In any event, assuming all of the above is not desired, then at path 164 a host processor 37 issued write command is to be executed by control unit 101. At decision step 165, space management determines whether or not it is an update write operation. if it is an update operation, now data is to replace currently stored data, then at function step 166, control unit 101 is commanded to erase the target area. A channel command retry signal is sent to host processor 37 by control unit 101 upon completion of step 165. Upon completion of the erasure at step 166, a DEVICE END signal is sent by control unit 101 to host processor 37 signalling completion of the erasure. Then the data is written to disk 30 at function step 177. Upon completion of function step 177, host processor 37 returns to other program steps (not shown) not pertinent to an understanding of the present invention.

if on the other hand at decision stop 165 space management determines that the data is original data and the write is not an update, then at decision step 170 space management determines whether or not there are any free and erased tracks ready for allocation. If not, then a track is erased as described with respect to Fig. 4 and is represented in Fig. 5 by stop 169. When a free and orased track is found by decision stop 170 or upon completion of the erasure stop 169, space manacqement at stop 171 allocates the track, to the write operation. Then tho write operation is actually performied at function step 177.

4- TL1907011-2- 8.

1 2 3 4 6 7 8 9 16 00000 0 13 000 D 21 4 23 24 26 21 28 22 23 24 26 27 While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. In particular, the invention may be applied to hard sectored media, fixed block architecture media, updatable media and the like.

Claims (14)

1. In a record medium for storing data, the medium having a large multiplicity of addressable rewritable data storage areas: the improvement including, in combination: a volume table of contents (VTOC) recorded on the medium for indicating the data contents of the medium; first indicia in VTOC for indicating allocated ones of the addressable data storage areas; second indicia in VTOC for indicating unallocated ones of the addressable data storage areas that are erased; 4 third indicia in VTOC for indicating unallocated ones of the addressable data storage areas that are not yet erased; and fourth indicia in VTOC indicating unformatted ones of the addressable data 15 storage areas that cannot receive data for storage until predetermined format signals St arc recorded therein, whereby the record medium is useable for recording and reading operations without requiring the entire medium to be initially formatted.

2. In the record medium set forth in claim 1, the improvement further including, S 20 in combination: 0 0 said second indicia being sorted by addresses of the respective data storage areas; and SI said fourth indicia constituting a single address of a one of the unformatted addressable data storage areas that is addressable by a lowest address of all the 25 addresses of the unformatted data storage areas.

3. In the record medium set forth in claim 1, the improvement further including, In combination: said record medium being a rotatable disk with a multiplicity of substantially circularly concentric tracks, each of said addressable data storage areas including a one of said tracks; i -31 one of said addrcssable data storage areas including a radially outwardmost one of said addressable data storage areas; and all of said first, second, third and fourth indicia being in said one addressable data storage area,

4. In the record medium set forth in claim 1, the improvement further including, in combination: said record medium being a record disk having a plurality of concentric record tracks with each of the record tracks having a single index indicia, each of said record tracks including a one of said addressable data storage areas; and each of said tracks that is represented by either of said first, second or third ,indicia having a home address record in immediate juxtaposition to the respective index indicia which home address record containing rotational locations of defects in the respective record tracks and all of the tracks represented by said fourth indicia not having said home address record. In the record medium set forth in claim 4, the improvement wherein the record medium has optically writeable and readable data storage areas. 20 6. A method of managing data storage space on a record disk comprising the 0 94 o 0 steps of: receiving a record disk having a multiplicity of concentric record tracks, each track having a readable index inlicia and indications of the circular extent of the track; C 25 initialising the record disk for data recording by the steps o7.: 9 I a) surface analysing a radially outward set of a predctermined number of said tracks, said predetermined number being substantially lcss than the total number of tracks on the record disk, indicating the location and extent of each detected surface defect; b) recording in each of th(e surface analysed tracks, indications of the rotational positions of surface defects In the respective surface analysed track; and *Igpi4~SIf -32- c) recording a volume tablc of contents in a radially outermost one of the said rccord tracks in said outward sct to contain thc addrcss of the tracks in the outward set as being free tracks available to be allocated for data storage and an indication that all of said tracks other than said outward set are not available for data storage until formatted.

7. Thei m~ethod set forth in claim 6, further including the steps after said initialising step of: placing the disk in an information handling environment by allocating ones of the free tracks for data storage, recording signals into and reading signals from ones of said alloca~ted tracks; recording in said volume table of contents which of formatted tracks are currently allocated for storage of data; when the disk is not being used for receiving signals to bc recorded or for 15 supplying recorded signals, formatting additional ones of said unformatted tracks 0 0 bcginning at a radial outermost one of the remaining unformatted tracks; and 0000 0 6 4 updating said volume table of contents to indicate a current radially outermost one of the remaining unformatted tracks and the additional ones of the tracks 'Ire available for data storage, o

8. The method set forth in claim 7, further including the steps after adupdatn 0 step of: 00 a* 0 deallocating ones of the allocated tracks which may contain data stored therein; when the disk is not being used for receiving signals to be recorded on the disk or for supplying recorded signals from thle disk, erasing free but not erased tracks; and recording In said volume table of contcnts which of thie free tracks have been crascd and which of the free tracks contain not erased data,

9. Ihe method set forth in claim 8, further including the steps after said recording step of: delaying formatting additional onies of said unformatted tracks until all of thle -33- free but not crascd tracks havc been erascd. A nmecthod set forth in claim 9, whcrcin said erasing and formatting performed when the disk is not being used arc limited to one track per operation, further including the step between any of said steps of: performing data recording and data readback operations and repeating said one track operation intcrmcdiate time spaced ones of said recording and rcadbaek operations,

11. The method set forth in claim 10, wherein said record disk has a magnetooptic recording area which requires erasurc oeforc recording, and said data recording 9 operation includes the steps of: a 0 updating a record in the magnetooptic recording area which is substantially less 'O 9 o, than the extent of a record track by delaying recording while erasing the portion to be 15 updated and then recording the updated portion on the erased portion of the record *track, '9 0

12. The method set forth In claim 11, wherein said updating step Includes the steps of: 0000o0 20 receiving an indication that signals arc to be recorded which are updates of o *currently recorded signals; identifying those portions to receive the updated signals and erasing those o portions; and then receiving the updated signal and recording same In the erased portions, 0 9 9

13. 11e method set forth In claim 10, said data recording operation Includes the steps of: receiving an updated set of data signals for data already recorded on the disk; allocating a freed and erased uttallocated track for receiving the updated data; recording the updated data onto the just allocated track; and erasing the data from the original track. -34- 1.4. In a data storage subsystem having a control unit including program means for operating the control unit and the subsystem, a disk recorder operatively coupled to the control unit and having a large capacity disk recording surface; the improvement including, in combination: operating program means including a program dispatcher in said control unit for effecting subsystem operation which includes recording data onto the large capacity disk surface and reading data recorded on the disk surface; formatting program means in the control unit, including surface analysis controlling program means and home address recording program means which records locations of defects In a respective track In a home address record in such track; ,said dispatcher having initialisation programing means operative to cause the control unit to check the large capacity disk surface to determine whether or not the disk surface has been initialised, and if not initialised, operative to activate the program means a given plurality of times for surface analysing and formatting a predetermined number of record tracks at a predetermined radial portion thereof and recording a volume table of contents (VTOC In a predetermincd one of said predetermined set of tracks; the dispatcher having further Intermediate format Initiating program means activated when the large capacity disk surface Is not currently being used for recording 20 or supplying readback signals from and to the control unit for activating said formatting program means to format a second predetermined number of sald unformatted record tracks, beginning with a radially outwardmost one of the unformatted record tracks; and said dispatcher cycling through all of Its operations such that said Intermediate 25 foromted program means is activated as a lower priority one of operations to be performed In the subsystem, in the subsystem set forth In claim 14, wherein said Intermediate formatting means selects a single record track to be surface analysed and formatted by said formatting program means. bi 7 4i 4 *r 4 .4 444 41 4 4 0 0r 0O 00 0* 0

16. In the subsystem set forth in claim 14, further including, in combination: erasure program means in the control unit actuatable by said dispatcher program means whenever said large capacity disk surface is not being used for recording data signals or supplying readback data signals for erasing data tracks on the large capacity disk surface which are not indicated as being used for data recording; allocation program means in the control unit for allocating ones of said record tracks for receiving data signals and indicating the allocated ones of the record track as being used for data recording and including means for recording the status of the tracks in said VTOC; and said dispatcher giving tihe erasure program means priority over said intermediate formatting program means.

17. In the subsystem set forth in claim 16, wherein said large-capacity disk 15 surface has an active recording layer which requires erasure before any recording,

18. In the subsystem set forth in claim 16, further including, in combination: program means in the control unit actuatable by said dispatcher to allocate a free and erased track to receive updated data for recording and maintaining the same 20 addressability for the updated data as is established for the originally recorded data, 19, In the subsystem set forth in claim 18, further including, in combination: said reallocating program means actuating said erasure programming means for erasing the old data track after the newly allocated record track has received the 25 updated data, In a machine-sensible and recordable record medium of the rotatable disk type for storing data, the medium having a large multiplicity of addressable data storage tracks which are concentrically arranged on the rotatable medium; the improvement including, in combination: a volume table of contents (VTOC) recorded on the record medium in a one 'il I~~26rl t

36- of said record tracks for indicating the data content and the current status of the record tracks on the medium; first machine-sensible indicating data stored in said VTOC for indicating allocated ones of the addressable data storage tracks; i 5 second machine-sensible indicating data stored in said VTOC for indicating I unallocated ones of the addressable data storing tracks; and fourth machine-sensible indicating data stored in said VTOC for indicating unformatted ones of the addressable data storing tracks that cannot receive data for storage until predetermined fcrmant signals are recorded therein such that the record medium is useable for machine-sensing and recording operations without initially ibrmatting the entire record i4;l 0 0 21. A data storage sysltm for storing and retrieving data with respect to a record 9 0 S, medium which has a multiplicity of addressable rewritable data storage areas which *S 15 arc initially prcsent.d in an unformatted record member entity, the system including .4 0 0 means for formatting portions of the medium and for reading and writing data in 0044 formatted storage areas under the control of a local or remote processor, means to maintain a volume table of contents (VTOC) recorded on the medium for Indicating the status and the data contents of the medium, including means to Indicate which 20 storage areas arc allocated ones of the addressable data storage areas; o 4 means to indicate which storage areas are unallocated ones of the addressable no 0 o data storage areas that are still storing data; and 00 00 0 o° means to Indicate which potential storage areas arc unformatted ones of the addressable data storage areas that cannot receive data for storage until predetermined 0 0 25 format signals are recorded thet.in and means by refereneo to the VTOC to 0 0 o progressively format the record medium between accesses to the data storage areas. 22, A system as claimed in claim 21, wherein the medium cannot be overwritten so that previously written storage areas must be erased before they can be rewritten, means for erasing allocated written storage areas between accesses and means to 4L i .^mmr- wvm~f^ M -37 update the VTOC to also show which allocated ones of the addressable storage areas have been erased. 23. A record storage member having a multiplicity of addressable record storage areas each of which is subject to defects, the improvement including, in combination: first machine-sensible control indicia on the storage member for indicating which of the addressable record storage areas have been initialised for identifying the existence of said defects within the respective addressable record storage areas; second machine-sensible control indicia on the storage member for indicating which of the addressable record storage areas have not yet been initialised; and third machine-sensible control indicia on the storage member for indicating which of said initialised addressable record storage areas have been allocated for 4.004 information-handling operations. o 15 24. In a machine-effected method of using a storage member having a recording So^ surface subject to defects and capable of having a maximal number of addressable data storage areas, including the machine-executed steps of: accessing a storage member which has no addressable data storage areas initialised for data recording; 20 initialising, including surface analysing, a predetermined number of the addressable data storage areas for any ensuing data recording, said predetermined number being less than the number of the addressable data storage areas; 00 0 o° conducting data processing operations with respect to the storage member which include recording data into the initialised addressable data storage areas; and 4 when the storage member is not participating in said data processing operations, initialising, including surface analysing, additional ones of said addressable data storage areas until the storage medium has said maximum number of initialised addressable data storage areas, 25. In the machine-effected method set forth in claim 24, further Including the machined-effectcd steps of: PlaJ6r~ila34,ldJt1~3t -38- accessing a storage member having a maximum of a multiplicity of addressable data storage areas; and selecting said predetermined number to be at least an order of magnitude less than said maximum number. 26. In the machine-effected method set forth in claim 25, further including the machine-effected step of: each time a one of the addressable data storage areas is initialised, generating a control record on the storage member indicating what portion of the storage member has yet to be initialised into addressable data storage areas. 27. In the machine-effected method set forth in claim 26, further including the *aO machine-effected steps of: 0 0 0. while performing said data processing operations and initialising the storage 15 member, keeping an electronic copy of the indication of said control record and 00 .performing said initialisation of additional addressable data storage areas from said electronic copy. 28. A record medium for storing data substantially as hereinbefore described with 0a.at 20 reference to the accompanying drawings. o ooaa 00 0 29, A method of managing data storage space substantially as hereinbefore 0 a described with reference to the accompanying drawings. 0 o a DATED this 1st day of March, 1991 INTERNATIONAL BUSINESS MACHINES CORPORATION By its Patent Attorneys DAVIES COLLISON '4 ttt'n~i3