JPH056888B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] The first track of the VTOC is assigned to DSCB4 and DSCB5, and the first track is read continuously when reading DSCB4, thereby collecting free space information at high speed. , the hashing method is used in search processing such as DSCB1 for data set access, determines the target track of the corresponding data set name, searches only on that track, and then searches the overflow track area. The overflow track area can be searched.

[Industrial application field]

The present invention relates to improvements in VTOC access methods. Note that VTOC is an area that manages data sets created on the DASD volume.

[Conventional technology]

Conventionally, when searching a VTOC, there have been methods of searching for keys sequentially from the beginning, or methods of using an index to locate within the VTOC and then searching for data.

[Problem to be solved]

However, the former method has the disadvantage that the channel occupancy time is long because the key search takes a long time, and the latter method requires the creation of an index and the processing of the index section. This has the drawback of increasing the number of I/Os and CPU time.

The present invention was created in view of this point, and aims to speed up VTOC access for searching data sets.

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the present invention.
The VTOC is divided into a first management area 1, a second management area 2 and an overflow track area 3. The first track of the VTOC is allocated to the first management area, and this track contains a format 4 data set control block DSCB4 and a format 5 data set control block DSCB4.
Data set control block DSCB5 is stored. A plurality of tracks are assigned to the second management area 2, including a format 1 dataset control block DSCB1, a format 2 dataset control block DSCB2, and a format 3 dataset control block DSCB1. Block DSCB3 is stored.

The format 1 data set control block DSCB1 is:
It shows the data set name, the characteristics of the data set, and the upper and lower limits of the created data set storage area. Format 2 data set control block
DSCB2 is created for the indexed sequential data set and is pointed to from the type 1 data set control block DSCB1. Format 3 data set control block DSCB3
is the format 1 data set control block DSCB1
It defines the data set storage area that could not be defined in . The format 4 data set control block DSCB4 defines the attributes of the VTOC itself. The format 5 data set control block is:
It manages the free space area.

In which track in the second management area 2 the format 1 data set control block DSCB1 for a certain data set is to be stored is determined by the hashing method. This hashing method is to divide the data set name by the number of tracks in the second management area 2, and use the remainder as the corresponding track number.

Information indicating whether or not the track is overflowing is written in the first record (record 0) of the track in the first management area 1. Similarly,
Record 0 of the track in the second management area 2 also has information written therein indicating whether or not the track is overflowing. For example, if a Format 1 data set control block DSCB1 is to be stored in a track in the second management area 2, and that track overflows, the Format 1 data set control block DSCB1 will be stored in the overflow track. Stored in area 3. Overflow track area 3 is allocated a small amount, for example 5 tracks.

〔Example〕

FIG. 2 is a diagram showing an example of the configuration of the VTOC in the present invention. In the same figure, 1 is DSCB4.
Management area where DSCB4 is stored, 2 is DSCB1 and
A management area where DSCB2 and DSCB3 are stored, and 3 represents an overflow track area. In addition,
DSCB is an abbreviation for Dataset Control Block.
The VTOC has a management area 1 that stores DSCB4 and DSCB5, a management area 2 that stores DSCB1, DSCB2, and DSCB3, and an overflow area 3. Management area 1
is the first track of VTOC, which includes
DSCB4 and DSCB5 are stored. DSCB4 is
It defines the attributes of the VTOC itself.
DSCB5 manages the free space area. Management area 2 is composed of a plurality of tracks, and DSCB1, DSCB2, and DSCB3 are stored therein. DSCB1 indicates the data set name, the characteristics of the data set, and the upper and lower limits of the created data set storage area. DSCB2 is created for an indexed sequential data set, which is
Pointed from DSCB1. DSCB3 is
This defines the data set storage area that could not be defined in DSCB1. The overflow area 3 is composed of, for example, five tracks. When the management area 1 track or the management area 2 track becomes full and the DSCB cannot be written, the
DSCB is written to overflow track area 3. Information as to whether there is overflow or not is written to the data section of record 0 at the beginning of the track. Note that DSCB0 is an empty DSCB.

The hashing method determines in which track within the management area 2 the DSCB1 of a certain data set is stored. In the hashing method, for example, the data set name is divided by the number of tracks in the management area 2, and the remainder is used as the corresponding track number. For example, if the remainder is 0, the DSCB1 is stored in the first track of management area 2, and if the remainder is 1, it is stored in the next track. The same applies to DSCB2 and DSCB3.

FIG. 3 is a diagram showing an example of the system configuration. In the figure, 4 indicates DASD, 5 indicates I/O supervisor, 6 indicates data management, and 7 indicates general program. The input/output macro command issued by the general program 7 is interpreted by the data management 6, which creates a CCW, etc., and starts the I/O supervisor 5. To request space allocation for a data set, use the general program 7
issues the ALLOCATE macro. Also, when reading/writing a dataset, first
Issue an OPEN macro, then issue a read/write macro.

FIG. 4 is a diagram illustrating allocation processing.
When the general program 7 issues the ALLOCATE macro specifying the data set name and number of tracks,
The following processing is performed under the control of the data management 6.

Read the first track of VTOC, that is, management area 1.

Read the corresponding track in management area 2 and check whether the same data set exists. If it does not exist, perform the following processing.

Search for DSCB0.

Sets the updating flag of DSCB4 and updates the DSCB0
Write DSCB1 above.

Write DSCB5.

Reset the updating flag of DSCB4.

When the general program 7 issues the OPEN macro, the data management 6 reads the corresponding tracks in the management area 1 and management area 2 of the VTOC, and in some cases the overflow track area 3, and reads the necessary tracks in the data control block. Performs processing to write information.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since DSCB4 and DSCB5 are stored together in the first track of the VTOC, free space information can be collected at high speed. Further, according to the present invention, for data set access,
The hashish method is used for search processing such as DSCB1,
Since the target track of the corresponding data set name is determined and only that track is searched, even if the number of data sets to be created increases, the search can be performed in a certain amount of time (short time), increasing speed. can be achieved. Furthermore, according to the present invention, a small amount of overflow track area is prepared, and when a track becomes unmanageable due to hash bias, a DSCB is written to the overflow track area, so that data set Management can be ensured.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram of the principle of the present invention.
FIG. 3 is a diagram showing an example of a VTOC configuration, FIG. 3 is a diagram showing an example of a system configuration, and FIG. 4 is a diagram explaining allocation processing. 1... Management area for storing DSCB4 and DSCB5, 2
...Management area for storing DSCB1, DSCB2, and DSCB3, 3...Overflow track area, 4...
DASD, 5...I/O supervisor, 6...Data management, 7...General program.

Claims (1)

[Claims] 1. The VTOC area is divided into a first management area 1, a second management area 2, and an overflow track area 3, and the first track of the VTOC is allocated to the first management area 1, This contains a format 4 data set control block (DSCB4) that defines the attributes of the VTOC itself, a format 5 data set control block (DSCB5) for managing free space, and a second management area. A format 1 data set control block (DSCB1) indicating the data set name, characteristics of the data set, and upper and lower limits of the created data set storage area is allocated to the data set 2. A format 2 dataset control block (DSCB2) created for an indexed sequential dataset and pointed to by the format 1 dataset control block (DSCB1), and a format 1 dataset control block (DSCB1) that cannot be defined. A format 3 data set control block (DSCB3) that defines the data set storage area that has been created, and a format 1 data set control block (DSCB1)
The data set name and the track in the second management area 2 in which the format 2 data set control block (DSCB2) and format 3 data set control block (DSCB3) are stored are determined in which track in the second management area 2. The data set control block is determined based on the number of tracks in the track, and information on whether or not the track has overflowed is stored in the first record of the track. A VTOC access method characterized by storing in overflow track area 3.