JPH04360069A - Method for controlling magnetic tape device - Google Patents

Abstract

PURPOSE:To avoid an impossible state for data access by recording in a rewritable area the index information of a data file which is recorded on a magnetic tape and additionally recording the same information as this index information on the leading end of the data file. CONSTITUTION:When the data correcting stage at the time of directory reproduction is informed from the magnetic device 1 to a control device 2, and the tape state of the directory part is judged deteriorated, the rewriting operation of the directory information on the magnetic tape is performed and the recovery of a recording state is attained; in addition, when the rewriting times of the directory information is in excess of a prescribed number, a directory replacement is performed and the reproducing impossibility of the directory information is prevented. Also, on the leading end of each data file the same information as the directory information is provided, and when the directory of the magnetic tape can not be reproduced, it is reproduced from the leading end making the restructuring of the directory possible, storing the information in a memory device 8, and enabling the reproduction of the data file on the magnetic tape.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape recording and reproducing device suitable for use in external storage devices of computers, and more particularly, to control for improving the integrity of index data for data retrieval on magnetic tapes. Regarding the method.

0002

2. Description of the Related Art As a conventional magnetic tape recording and reproducing system, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-31742, a random access memory is provided in a magnetic tape device to store information in a rewritable area (hereinafter referred to as a directory). Although it describes a method of shortening data access time by having it on a magnetic tape device, it does not discuss how to protect directory information on magnetic tape.

0003

[Problems to be Solved by the Invention] The above-mentioned prior art does not take into consideration the deterioration of data in the directory section provided on the magnetic tape and the situation where it cannot be reproduced, and the directory section is damaged by the tape pass or the like. If the number of errors increases and the directory information cannot be reproduced, there is a problem in that the data recorded on the tape cannot be reproduced. A magnetic tape device (hereinafter referred to as DAT-MS), which is an external storage device for computers that applies digital audio tape recorder technology, has a means that makes it possible to partially rewrite already recorded data. In the case of a device with a large capacity, it is possible to shorten the access time for recorded data files by providing a directory at the head of the magnetic tape and using the directory information. However, with DAT-MS, a large capacity of data of about 1 gigabyte can be recorded on a single roll of magnetic tape, so the number of files increases, and the number of tape passes in the directory section is greater than in the section where normal data files are recorded. will increase significantly, increasing the chance of receiving damage. Therefore, even if the data file is in a readable state, if the directory information becomes unreadable, the data file also becomes unreadable.

[0004] In general magnetic tape devices, data is not accessed using a directory, but the beginning of the data file is played back in order from the beginning of the tape to search for the desired data. If the data capacity of one roll is large and it takes time to start playback after stopping, this method of data access may cause problems when attempting to play back data near the end of the tape. It takes more time than the playback time of one tape (more than two hours for DAT-MS). It is fine if this playback operation is for an emergency purpose such as backing up the hard disk, etc., but if the playback operation is included in normal operation, it will take too much time, and data access using the directory is necessary to shorten the operation time. It is.

An object of the present invention is to notify the control device from the magnetic tape device of the data correction stage during directory playback, so that when it is determined that the tape condition of the directory section has deteriorated, the directory information is transferred to the magnetic tape. An overwrite operation is performed to recover the recording state, and furthermore, when the number of overwrites that the directory has as information exceeds a predetermined number, a directory replacement operation is performed to avoid a state in which directory information cannot be reproduced. be. In addition, by providing information similar to directory information at the beginning of each data file, even if the directory on the magnetic tape becomes unplayable, the directory can be rebuilt by playing the magnetic tape from the beginning. The object of the present invention is to provide a means for reproducing data files on a magnetic tape by storing directory information in a separate memory device.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention adds index information of each data file placed on a directory to the beginning of the data file and records it on a magnetic tape. By dispersing and recording the information twice, even if the directory itself becomes unplayable, it is possible to reconstruct the directory by sequentially playing back the data files. An identification code is placed at the beginning of the index information added to the beginning of the data file to distinguish it from other data, and a terminal code is placed at the end of the data file to indicate the end of the data.
When recording the next data file, this terminal code is overwritten and recorded so that the delimiter and end of each data file can be identified. Reduced the possibility of misrecognition with other data.

[0007] A predetermined multiple of the required capacity is secured in advance as a directory area to be placed on a magnetic tape, and error correction information and the number of overwrites during playback of the directory section are placed in the tape information in the directory information, and the directory section is overwritten. By updating this number of times each time an operation is performed, the state of data deterioration in the directory section is kept as a record, and if the number of overwrites exceeds a predetermined number, the directory is reserved in advance as a directory area while it can be played back. Replace it with another position. The original directory section is overwritten with an identification code as an unusable area so that it will not be used again, thereby reducing the possibility that the directory cannot be reproduced. Furthermore, by placing a gap between directories to be replaced that is larger than the length of the tape that contacts the recording/reproducing head, damage caused by the tape pass when another directory section is accessed is avoided.

[0008]

[Operation] After confirming that a magnetic tape is inserted into the magnetic tape device, the control device connected to the magnetic tape device issues a data reproduction command to the magnetic tape device to reproduce the directory section. If the directory information is normally reproduced, it is confirmed that the data transferred from the magnetic tape device in response to the data reproduction command is directory information, and then stored in the RAM (random access memory) of the control device. Subsequently, the error correction information at the time of directory section reproduction transferred from the magnetic tape device is acquired. If the error correction information is less than a predetermined value, data file recording and playback operations are performed based on the directory information stored in RAM, and if additional data file recording is performed, the directory is updated at the end of processing. Perform rewriting.

[0009] If the error correction information exceeds a predetermined value, it is determined whether the number of directory overwrites in the directory information stored in the RAM exceeds a predetermined value. If the number of overwrites is less than a predetermined value, the RAM
Add 1 to the above number of overwrites and issue a recording command to the directory location to the magnetic tape device. After the recording order is issued;
By transferring the directory information stored in the RAM as data to be recorded to the magnetic tape device, the directory information on the magnetic tape is overwritten. If the recorded data on the magnetic tape is damaged by the tape pass during the directory playback operation, errors during data playback can be reduced to some extent by performing an overwrite operation to re-record the data on the magnetic tape. However, if the magnetic tape itself is damaged and errors increase, recovery by overwriting cannot be expected. In this case,
Change the recorded location of the directory and replace it with the undamaged part. The number of times the directory section in the directory information is overwritten is used as a judgment for performing this replacement process.

[0010] When the error correction information exceeds a predetermined value and the number of directory overwrites also exceeds a predetermined value, it is indicated that the magnetic tape position where directory information was previously recorded is an unusable directory. Information is recorded, and the directory information stored in the RAM is recorded in another location prepared in advance as a directory section. If there is no other location left where the directory should be rewritten, leave the directory information as it is and do not replace the directory until the magnetic tape you are using reaches its usage limit. The user is prompted to use another magnetic tape.

[0011] If data correction becomes impossible during the directory playback operation of the control device and the directory information cannot be played back normally, or if the playback directory information is unusable, the next directory section is played back and prepared in advance. The same operation is repeated until there are no more directory parts left. Processing when directory information is not obtained even with this operation will be described below.

(1) Operation when recording a data file When additionally recording a data file while the directory information is normally reproduced and the directory information is stored in the RAM of the control device, the data file is recorded on the magnetic tape. The index information of the data file including the starting position of the data file, the size of the data file, etc. is generated and added to the directory information on the RAM. Next, an identification code indicating the beginning of the data file and the above index information are added to the beginning of the data file, and an identification code indicating the end of the data is added to the end of the data file. Here, the recording head position of the data file indicates the position of the end identification code of the data file that is already recorded on the magnetic tape and is at the final position in the forward direction of the magnetic tape. After generating a data file with an identification code and directory information added, the control device issues a data recording command to the magnetic tape device, and then the data of the additionally generated data file is transferred to the magnetic tape device and recorded on the magnetic tape. is recorded from the above-mentioned first position.

(2) Operation when reproducing a directory If a directory on a magnetic tape recorded using the recording method becomes unreproducible, data is reproduced from the beginning position where a data file is recorded on the magnetic tape. After confirming that the beginning of the reproduced data is the data file start identification code, the next data is stored in RAM as index information, and then moved on the magnetic tape by the amount of data file capacity included in the index information. Play. Here, if the beginning of the reproduced data is the identification code at the beginning of the data file, the same operation is repeated until the index information is additionally stored in the RAM and the end code is reached. The directory information created in the RAM by this operation is stored in another memory device with an identifier corresponding to the magnetic tape on which this operation was performed.

[0014] With the above control, it is possible to access data files on a magnetic tape by referring to the re-created directory information even on a magnetic tape whose directory cannot be reproduced.

[0015]

Embodiments Hereinafter, embodiments of this apparatus will be explained with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a magnetic tape device control method according to the present invention, in which 1 is a magnetic tape device, 2 is a control device for the magnetic tape device, 3 is a magnetic tape recording/reproducing unit, and 4 is a magnetic tape device control device. a controller, 5 a SCSI (small computer system interface), 6 a buffer RAM, 7 a data correction unit, 8 a memory device,
9 is a RAM, 19 is a display device, and 20 is an input device. In the figure, a control device 2 sends various commands such as data recording and data reproduction to the magnetic tape device 1. In the magnetic tape device 1, commands sent from the control unit 1 are sent to the controller 4 via the SCSI 5, and the controller 4 interprets the received commands and executes operations according to the commands.

In the case of data recording, the control device 2 sends S
A data recording command and data specifying the position on the magnetic tape where the data should be recorded (hereinafter referred to as position data) are sent via the CSI 5, and then data to be recorded on the magnetic tape (hereinafter referred to as recording data) is sent. send. Recorded data is stored in buffer R, which is an internal buffer in magnetic tape device 1.
Stored in AM6. Then, based on the data recording command, the controller 4 stores the buffer RAM 6 and the data correction unit 7.
and generates an error correction code (parity) for the recorded data stored in the buffer RAM 6 and adds it to this recorded data. When this process is finished, the buffer RA
Recorded data to which parity has been added is stored in M6. Next, under the control of the controller 4,
The recording and reproducing section moves the magnetic tape back and forth while reading the position information already recorded on the magnetic tape to move the magnetic tape to the position designated by the position data. When the magnetic tape reaches the designated position, under the control of the controller 4, the parity-added recording data in the buffer RAM 6 is subjected to parallel/serial conversion and transferred to the recording/reproducing section 3 as serial data. In the recording and reproducing section 3, the above-mentioned parity generation and
If the additional processing is the first parity generation/addition processing, then the second parity generation/addition processing, interleaving, etc. similar to DAT recording and reproducing audio signals are performed, and the data is recorded at a specified position on the magnetic tape. Data is recorded.

In the case of data reproduction, the control device 2 sends the SC
A data reproduction command and position data on the magnetic tape of data to be reproduced are sent to the controller 4 via the SI 5. The controller 4 controls the recording and reproducing section 3 according to the data reproducing command, moves the magnetic tape to the position specified by the position data, and reproduces the data recorded on the magnetic tape from the specified position. This reproduced data (hereinafter referred to as reproduced data) is subjected to processing such as interleaving and error correction using the parity added by the second parity generation/addition process, and then processed under the control of the controller 4. The data is then stored in the buffer RAM 6. The error correction performed here is performed in units of tracks on the magnetic tape, and the number of parity errors (number of block errors) detected during parity check for each of the 128 blocks (PCM data section) that make up one track is counted. It is possible,
The counted number of block errors is held in the controller 4 as error correction processing information. Then, the data correction unit 7 performs error correction using the parity added by the first parity generation/addition process. After that, this playback data is read out from the buffer RAM 6,
It is transferred to the control device 2 via the SCSI 5. here,
The error correction process by the data correction unit 7 is carried out by the recording/reproducing unit 3.
The error correction processing information is used to determine whether or not the error correction has been performed by the data correction unit 7 (hereinafter, the case where correction has been performed is referred to as C3 correction). It is held in the controller 7 along with the number of block errors, and is transferred to the control device 2 via the SCSI 5 according to a command from the control device 2. Note that the error correction method by the data correction unit 7 is D.
For AT-MS, Reed-Solomon RS (38, 32
, 7) is used. In addition, interleaving improves the data correction ability for burst errors that span tracks on the magnetic tape. In addition, the data correction section 7
If error correction becomes impossible even with
(The response from the controller 2 to the controller 2 is called the status), and no data is transferred. In this case, data cannot be reproduced.

[0018] On magnetic tape, two tracks constitute one frame.
One group consists of 32 frames, and in each group,
It is formatted as 4 frames as a gap frame, 23.5 frames as a data frame, and 4.5 frames as a parity frame. Error correction by the data correction unit 7 is performed in units of one group, and the records recorded in the data frame Parity is generated, added, and error corrected for each data. Record data for one group is supplied from the control device 2, and the record data for each group is recorded in a data frame on the magnetic tape, and the parity generated for the record data indicates that this record data is recorded. It is recorded in the parity frame of the same group. Here, one group of recorded data and reproduced data, which is a unit of error correction, is 128 Kbytes of data.

Depending on the recording format, the magnetic tape device 1 can overwrite and rewrite data already recorded on the magnetic tape by recording and reproducing data on the magnetic tape in units of groups.

The above is an explanation of the operation of the magnetic tape device 1. In this embodiment, a predetermined number of groups at the beginning of the magnetic tape are set in advance as directory areas, and subsequent groups are set as actual data file recording areas. In the control method of the magnetic tape device 1 used, the integrity of directory information recorded on the magnetic tape is improved.

FIG. 2 shows the directory on the DAT tape and the recording format of the data file. 10 is D
AT tape, 11 is a data file containing data to be recorded and reproduced, 12 is a directory recorded at the beginning of the DAT tape, and 13 is index information of the data file 11 contained in the directory. In FIG. 2, the directory 12 is secured in advance with three areas at the beginning of the DAT tape 10, and each directory 12 is spaced apart from each other so as not to be damaged by recording/playback operations of other directories. Set. Next, FIG. 3 shows an example of the contents of the directory 12, data file index information 13, and data file 11. 14 is a directory identification code, 15 is a data file capacity, 16 is a data file starting position, 17 is a starting identification code, 18 is an end identification code, and 21 is information on the number of times the directory is overwritten. FIG. 4 shows a processing flow when reproducing a directory. The directory reproducing operation from the DAT tape 10 at the time of starting the operation of the control device 2 will be described below with reference to FIG.

At the beginning of the operation, the control device 2 issues a command to the magnetic tape device 1 to determine whether a tape has been inserted into the magnetic tape device 1 and is ready for operation. If the magnetic tape device 1 returns an operable status in response to this command, the control device 2 issues a data reproduction command to reproduce the first directory 12 on the DAT tape 10. It is determined whether the status returned in response to this data reproduction command is that reproduction is not possible, and if reproduction is not possible, the control device 2 issues a data reproduction command to reproduce the next directory 12. If all three directories 12 become unplayable, the display device 19 notifies the user of this condition, and the input device 20
The user is prompted to input the identifier of the DAT tape currently in use, and the corresponding directory information is searched on the memory device 8. If there is corresponding directory information on the memory device 8, store that directory information in the RAM 9,
Terminates the directory playback operation and executes the next process. If there is no corresponding directory information on the memory device 8, it is displayed on the display device 19, and the user is asked to input from the input device 20 whether or not to recreate the directory. If the directory is not to be recreated, all processing ends.

If any of the directories 12 is successfully reproduced, the reproduced data transferred from the magnetic tape device 1 as reproduced data is stored in the RAM 9, and the directory identification code at the beginning of the directory information stored in the RAM 9 is stored. 14 is correct. If it is different, it is determined that the inserted DAT tape is not a tape for the control device 2, and a message is displayed on the display device 19 to display the DA tape.
The user is asked to input from the input device 20 whether or not to initialize the T tape. If tape initialization is not performed, all processing ends. When initializing the tape, RAM9
Creates a new directory, ends the directory playback operation, and executes the next process.

If the directory identifier 14 is correct, then the number of block errors and C3 correction information are obtained from the magnetic tape device 1 as error correction information during directory reproduction. If the obtained number of block errors is less than the predetermined number and C3 correction is not performed, it is determined that the recorded state of the reproduced directory 12 is good, the directory reproduction operation is ended, and the next process is performed. Execute. The number of block errors transferred here is obtained by the total of data frames and parity frames in one group, and in this embodiment, 320 is the threshold value. (If there are all errors, it will be 7168) If this number of block errors exceeds the threshold value or if C3 correction is performed, the number of directory overwrites 21 of the directory information 12 stored in the RAM 9 will increase to a predetermined number. Determine whether or not it exceeds. If the number of overwrites 21 is less than a predetermined value, 1 is added to the value of the number of overwrites 21 in the RAM 9, and a data recording command is issued to the magnetic tape device 1 to record the data at the same position on the DAT tape as the reproduced directory 12. Then, the directory information in the RAM 9 is transferred to the magnetic tape device 1, thereby overwriting the directory information on the magnetic tape. In this embodiment, the number of overwrites is limited to three times.

[0025] If the number of overwrites exceeds a predetermined number,
Performs a directory replacement operation. At this time, if there is space left to replace the directory,
The directory identification information in the RAM 9 is replaced with data indicating that the directory area is unusable, and is recorded at the same position on the DAT tape as the reproduced directory. Thereafter, the directory identification information in the RAM 9 is set to a correct value, the number of overwrites 21 is set to 0, and the information in the RAM 9 is recorded at the next directory recording position.

If there is no area left to replace the directory, the display device 19 displays that the tape currently in use is at its usage limit, and notifies the user to store the directory information in the memory device. Memory device 8
When storing directory information in the input device 20
The identifier of the DAT tape in use is input from , and this identifier is added to the directory information in the RAM 9 and stored in the memory device 8 .

By reproducing the directory under the above control, it is possible to reduce the possibility of a situation in which the directory becomes unreproducible and therefore the data on the tape cannot be reproduced.

Next, a description will be given of processing related to a method for recovering directory information when directory information cannot be reproduced even with this control.

[0029] The directory is reproduced normally and the RAM9
As shown in FIG. 3, the data file 11 that is additionally recorded on the DAT tape with the directory information stored therein includes a first identification code 17 from the beginning of the data, and index information 13 of the data file registered in the directory information section. is recorded on the DAT tape in the recording format shown in FIG. Here, when recording on the DAT tape, a new data file is additionally recorded so as to overwrite and erase the termination identification code at the end of the last data already recorded on the tape. As a result, the data files recorded on the magnetic tape are classified by the start identification code, and the end identification code is present only at the end of the data. If the directory of the tape recorded in this way becomes unplayable, the data file 11 shown in FIG.
3 are sequentially stored in the RAM 9 and moved on the magnetic tape by the capacity of the data file capacity 15 in the index information 13. By repeating this operation until the end identification code 18 is found, the directory information that cannot be reproduced is recreated in the RAM 9. In this case, directory 12
Although the information attached to the tape at the beginning of the directory cannot be played back, the index information used when searching for data files on the tape is played back, so if the directory becomes unplayable, the data file cannot be played either. . The created directory information has a tape identifier inputted from the input device 20, and by adding this identifier and storing it in the memory device 8, the information on the DAT tape can be stored on the DAT tape without having to recreate the directory. It becomes possible to access the data file.

[0030]

According to the present invention, in controlling a magnetic tape device, it is possible to reduce the possibility of a situation in which data access is not possible due to the inability to reproduce a directory when data is accessed using a directory on a magnetic tape. It is possible to provide a means that enables directory recovery and data access using the directory information even if the directory cannot be reproduced.

[Brief explanation of drawings]

[Fig. 1] Block diagram of a control device of a magnetic tape device.

[Figure 2] Recording format diagram on DAT tape,

[Figure 3] An explanatory diagram of the contents of each information,

FIG. 4 is a processing flowchart when playing a directory.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Magnetic tape device, 2...Control device, 3...Recording/reproducing device, 4...Controller, 5...SCSI,
6... Buffer RAM, 7... Data correction section,
8...Memory device, 9...RA
M, 19...display device, 2
0...Input device.

Claims (3)

[Claims] 1. A magnetic tape device capable of providing a rewritable area at the beginning of a magnetic tape, in which index information of a data file to be recorded on the magnetic tape is recorded in the rewritable area; A method for controlling a magnetic tape device, characterized in that when a file is recorded on the magnetic tape, information similar to index information recorded in the rewritable area is added and recorded at the beginning of the data file. 2. According to claim 1, the data is recorded by adding a correction code when recording data on the magnetic tape, and the error correction status of data correction processing is performed using the correction code when reproducing the data. . A control method for a magnetic tape device, which can notify a control device connected to the magnetic tape device as information, and overwrites the rewritable area on the magnetic tape based on the notified error correction information. 3. In claim 2, the number of overwriting operations is stored in the rewritable area as information, and the tape deterioration state of the rewritable area is determined based on the number of overwriting operations, and the rewritable area is separated. A method of controlling a magnetic tape device that replaces the position of