JP2595096B2 - Control method of magnetic tape unit and buffer memory - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape device, and more particularly, to a magnetic tape device having a function of rewriting already recorded data and a control method of a buffer memory.

[Conventional technology]

In a magnetic tape device, data is normally recorded in order from the head of the tape. When recording new data on a magnetic tape, so-called append-type recording is performed, in which new data is recorded following the last part of previously recorded data.

JP-A-63-251971 rewrites already recorded data in a magnetic tape device. A method that enables a so-called update-in-place recording is disclosed. In this method, a block in which data is grouped in an appropriate unit is formed, and recording and reproduction are performed on a magnetic tape in units of this block. On the magnetic tape, an amble of an appropriate length is recorded between blocks.

An outline of data recording by the update-in-place method will be described with reference to FIG. FIG. 10A shows the format of a magnetic tape when the update-in-place method is used. Reference numerals 101, 102, and 103 denote blocks in which the above-described data is collected in appropriate units. An amble is recorded between these blocks. Block (n
-1) An amble 104 exists between 101 and block (n) 102
However, an amble 105 is recorded between the block (n) 102 and the block (n + 1) 103. These ambles have a length of L here. A case in which, for example, block (n) 102 is rewritten among these blocks will be described. As shown in FIG. 10 (b), recording is performed in such a manner that ambles 107 and 108 each having a length of 1/2 L are added before and after data 106 to be newly recorded in the block (n) 102. When this data is recorded on a magnetic tape having the format shown in FIG. 10 (a), the result is as shown in FIG. 10 (c). In this case, the recording start position 109 and the recording end position 110 of the data (including the amble) to be rewritten are in the amble areas 104 and 105. Therefore, even if the rewriting start position is shifted back and forth to half the length L of the amble 104, the rewriting may cause the overwriting of the data of the preceding and succeeding blocks or the rewriting of the block, in this case the block (n The old data of 102 does not remain. Therefore, the length L of the amble in the format of the magnetic tape is determined in consideration of the shift amount of the write start position.

As described above, also in the magnetic tape device, a method has been devised which enables data already recorded on the magnetic tape to be rewritten in units of a certain unit and in units of blocks in the above example.

In a magnetic tape device, a buffer memory is used to reduce the time required for recording data on a magnetic tape. In a magnetic tape device, when data is recorded on a magnetic tape, it takes time to perform positioning processing to a recording start position. The buffer memory is for reducing the number of times of positioning processing to the recording start position. For example, when the unit for recording data on the magnetic tape is a block, data to be recorded is stored in a buffer memory instead of sequentially recording data on the magnetic tape for each block, and several blocks are collectively recorded on the magnetic tape. Record. Accordingly, it is not necessary to perform positioning to the recording start position for each block, and it is possible to shorten the time required for data recording by that amount.

FIG. 2 shows a configuration when a buffer memory is used. A buffer memory 12 is provided between the magnetic tape device 11 and a host computer 13 that uses the magnetic tape device 11 as a storage device. The magnetic tape device 11 and the buffer memory 12 are connected by a bus 14, and the buffer memory 12 and the host computer 13 are connected by a bus 15. The operation of the buffer memory will be briefly described with reference to FIG. Fig. 11 (a)
Indicates the format of the magnetic tape. Block (n-
1) It is assumed that 131, block (n) 132, and block (n + 1) 133 are sequentially recorded from the head of the tape. It is assumed that the buffer memory 12 is not connected and the host computer 13 and the magnetic tape device 11 are directly connected by the bus 15. As shown in FIG. 11 (b), the host computer 13 sends data 134 to be recorded in the block (n-1) 131, data 135 to be recorded in the block (n) 132, and block (n + 1) 133 via the bus 15. 134 to be recorded in
Is transferred to the magnetic tape device 11. For example, there is a temporal gap 125 shown between data 134 to be recorded in the block (n-1) 131 and data 135 to be recorded in the block (n) 132. Occurs. This time, the host computer
Reference numeral 13 denotes a time required for preparing data 135 to be recorded in the block (n) 132. However, when such a time gap occurs, the magnetic tape device 11 records the data 134 in the block (n-1) 131, then temporarily stops the tape from running at the position indicated by 122, and returns to the block (n) 132. With the data 135 to be recorded being transferred, positioning to the recording start position is performed when the transfer of the data 135 is started,
Data recording to the block (n) 132 is performed.
As described above, when the host computer 13 cannot continuously transfer the data to be recorded on the magnetic tape to the magnetic tape device 11, the magnetic tape device 11 stops running the magnetic tape and starts recording each time. It is necessary to perform positioning to the recording start position. On the other hand, FIG. 11 (c) shows a case where the buffer memory 12 is connected between the magnetic tape device 11 and the host computer 13. Even if the data transferred from the host computer 13 to the buffer memory 12 has the same timing as that shown in FIG. 11B, the data is temporarily stored in the buffer memory 12 so that the data is transferred from the buffer memory 12 to the magnetic tape device 11. The data to be provided can be continuous. The data transferred on the bus 15 includes data 134 to be recorded in the block (n-1) 131, data 135 to be recorded in the block (n) 132, and data 136 to be recorded in the block (n + 1) 13. Even if it is transferred in the form of being held, it is temporarily stored in the buffer memory 12 so that when it is transferred to the magnetic tape device 11 through the bus 14, the block (n-1) 131
To the data 136 to be recorded in the block (n + 1) 133 are continuous. Thus, in the magnetic tape device 11, the recording start position 121 of the block (n-1) 131 is shifted from the recording end position 12 of the block (n + 1) 133.
Up to 4, recording can be performed continuously without stopping the tape, and the number of times of positioning to the recording start position can be reduced as compared with the case where the buffer memory 12 is not connected. If the capacity of the buffer memory is large, it is possible to reduce the number of times of positioning to the recording start position.

Regarding the method of shortening the data recording time by the buffer memory in such a magnetic tape device, for example, the latest magnetic recording technology and device / equipment, the latest magnetic recording technology and device / equipment editing committee (General Technology Publishing Company) Chapter 3,
"3.1 / 2 inch streamer type magnetic tape device".

[Problems to be solved by the invention]

As described above, the buffer memory is used in the magnetic tape device to shorten the data recording time.

In a magnetic tape device using such a buffer memory, consider a case where data recording is performed by an update-in-place method as disclosed in the above-described related art.

FIG. 12A shows a tape format including an area in which data is recorded by the update-in-place method and an update-in-place area. In this example, after five blocks from block (n) 141 to block (n + 4) 142 are recorded by the update-in-place method, recording is performed also from block (n + 5) 143 to block (n + 9) 144 by the append method. It is a thing. In this state, the host computer 13
Consider the case where data recording processing is instructed in the following order. (1) Four blocks from the block (n + 10) 145 to the block (n + 13) 146 are recorded with the append method. (2) Data is recorded in block (n + 2) 140 by the update-in-place method. (3) Following the data recorded in (1), four blocks from the block (n + 14) 147 to the block (n + 17) 148 are recorded in the append system. By these processes, the data recording state on the magnetic tape is as shown in FIG. 12 (b). When these processes are performed, data to be recorded on the magnetic tape is stored in the buffer memory in the form shown in FIG. 12 (c). That is, data 149 to 150 to be recorded from block (n + 10) 145 to block (n + 13) 146, data 151 to be subsequently recorded to block (n + 2) 140, and block (n + 14) 147 to block (n + 1)
7) The data 152 to 153 to be recorded by 148 are stored in the buffer memory in the form. It is assumed that the data stored in the buffer memory is recorded on a magnetic tape by the magnetic tape device 11. As shown in FIG. 12 (d),
In this case, first, the recording start position is positioned at the position 154, and the block (n + 10) 145 to the block (n
+13) Record 146. Subsequently, block (n + 2) 140
In order to record data on the recording position, the recording start position is determined at the position 155. After recording the block (n + 2) 140, the recording start position is determined at the position 156 to record the block (n + 14) 147 to the block (n + 17) 148. Although the buffer is connected to the memory in this manner, the number of times of positioning the magnetic tape at the recording start position does not decrease, and the data recording time cannot be reduced.

These issues are being updated and
This occurs when performing in-place recording, that is, when re-recording data that has already been recorded. When re-recording data recorded by these update-in-place methods and additionally recording data by append data recording, the respective recording areas are separated from each other on the magnetic tape. Only, the number of times of positioning to the recording start position increases.

As described above, the conventional magnetic tape device has a problem that the buffer memory does not function effectively when performing data recording by the update-in-place method.

An object of the present invention is to provide a magnetic tape device and a buffer which can reduce the number of times of positioning to a recording start position by connecting a buffer memory even in a magnetic tape device which performs data recording by an update-in-place method. An object of the present invention is to provide a memory control method.

[Means for solving the problem]

The purpose is to store the data stored in the buffer memory,
When adding data indicating whether the data is recorded in the update-in-place method or in the append method, and recording the data from the buffer memory to the magnetic tape, the append method is used. After the recording of the data to be recorded on the magnetic tape is completed,
This is achieved by controlling to record data to be recorded by the update-in-place method.

[Action]

If there are areas on the magnetic tape where data is to be recorded by the update-in-place method and areas where data is to be recorded by the append method, the areas must be separated on the magnetic tape as described above. Becomes Each of the data stored in the buffer memory
When adding data indicating whether the data is data to be recorded by the update-in-place method or data to be recorded by the append method, and recording the data from the buffer memory to the magnetic tape, By referring to the information, first, data to be recorded in the append system is collectively recorded. In this case, the data to be recorded in the append mode is updated in-between.
If you do not insert the data to be recorded by the place method,
This is data that is continuously recorded on a magnetic tape. Therefore, all the data stored in the buffer memory and recorded by the append method can be recorded by positioning one data at the recording start position.
Subsequently, data to be recorded by the update-in-place method which is not recorded but is held in the buffer memory is recorded on the magnetic tape. As a result, at least the positioning to the recording start position for recording the data to be recorded by the append method on the magnetic tape needs to be performed only once, and the number of times of positioning to the recording start position can be reduced. It is possible to shorten the recording time.

〔Example〕

An embodiment of a magnetic tape device and a control method of a buffer memory connected thereto according to the present invention will be described in detail with reference to the drawings.

The magnetic tape device and the buffer memory are connected as shown in FIG. The magnetic tape device 11 is connected by a bus 14 to a buffer memory 12, and the buffer memory 12 is connected by a bus 15 to a host computer 13 using the magnetic tape device 11 as a storage device.

FIG. 1 shows a flow of processing for recording data on a magnetic tape in the configuration of FIG. First host computer 13
Transfers the data to be recorded on the magnetic tape to the buffer memory 12 through the bus 15 (step 1). Buffer memory
In step 12, the transferred data is data to be recorded on a magnetic tape by the append method,
Information indicating whether the data is data to be recorded on a magnetic tape by the place method is added and stored in the buffer memory 12 (step 2). The magnetic tape device 11 first receives, from the data stored in the buffer memory 12, data to be recorded on the magnetic tape by the append system in order through the bus 14, and records the data on the magnetic tape (step 3). At this time, the information added in step 2 is used. After all the data to be recorded on the magnetic tape by the append method stored in the buffer memory 12 is recorded on the magnetic tape, the data is recorded on the magnetic tape by the update-in-place method stored in the buffer memory 12 The data is received through the bus 14 and recorded on a magnetic tape (step 4).

FIG. 3 shows an embodiment in which data to be recorded by the update-in-place method is distinguished from data to be recorded by the append method in the buffer memory 12 using a flag.

FIG. 3A shows the processing of the host computer 13 in the data transfer from the host computer 13 to the buffer memory 12. The host computer 13 first checks whether there is a free area in the buffer memory 12 (step 51), and if there is a free area, transfers one block of data to the buffer memory 1 (step 52). These processes are repeated until the transfer of all data to be recorded on the magnetic tape is completed (step 53). The above processing is processing corresponding to step 1 in FIG. FIG. 3B shows the processing in the buffer memory 12 at this time. Each time one block of data is received (step 54), the buffer memory 12 determines whether or not the data is a block to be recorded by the update-in-place method (step 55). A flag indicating that the data is to be recorded by the update-in-place method if the block performs data recording by the place-method (update-in-place-data)
(Step 56), and if the data is data to be recorded by the append method, a flag (append flag) indicating that the data is data to be recorded by the append method is added (step 57). Store in 12. All these data to be recorded on the magnetic tape are stored in the buffer memory 12 like the host computer 13.
(Step 58). The above processing is processing corresponding to step 2 in FIG.

The configuration of the buffer memory at this time is not limited as long as it can store the data together with the number of the block for recording the data and the flag. For example, as shown in FIG. 4A, an area 61 for storing a block number at the head of each data 63 stored in the buffer memory.
And an area 62 for storing a flag indicating whether to perform data recording by the update-in-place method or data recording by the append method. As shown in FIG. 4 (b), an area 64 for storing data to be recorded on the magnetic tape, an area 65 for storing a block number for recording the data, and whether the recording is performed by the update-in-place method or not. An area 66 for storing a flag indicating whether to perform recording according to the method may be provided separately and managed in association with each other.

FIG. 5 shows a data transfer process from the buffer memory 12 to the magnetic tape device 11. Although not shown, the magnetic tape device 11 records the transferred data on a magnetic tape. First, N is set to 1 (step 71). Where N
Is a value indicating the order in which the data stored in the buffer memory 12 is transferred from the host computer 13. That is, when N = 1, the host computer 13 indicates the data of the block first transferred to the buffer memory 12, and when N = 2, it indicates the data transferred to the buffer memory 12 next. The magnetic tape device 11 first checks the flag of the data first transferred from the host computer 13 stored in the buffer memory 12, that is, the flag of N = 1 data (step 72). If the append flag is set in the flag, it is transferred to the magnetic tape device 11 (step 7).
3). Although not shown, the magnetic tape device 11 records the transferred data on a magnetic tape. Subsequently, 1 is added to N (step 74), and it is checked whether all data stored in the buffer memory has been processed (step 7).
5) Repeat the above processing until all data processing is completed. After all the processes for the data stored in the buffer memory 12 are completed, the data in which the update-in-place flag left in the buffer memory is set is transferred to the magnetic tape device 11 (step 7).
6).

The above process will be specifically described with an example in which data is recorded on the magnetic tape shown in FIG.

In FIG. 6, block (n) 21 to block (n)
+3) Four blocks up to 22 are blocks recorded by the update-in-place method in the past. Six blocks from block (n + 4) 23 to block (n + 9) 24 are blocks recorded in the past by the append method. As described above, in the case of the update-in-place method, amble parts 25, 26, 27, 28, and 29 are recorded between blocks. A case in which data recording processing is performed on the magnetic tape in accordance with an instruction from the host computer 13 will be described. (1) After the block (n + 9) 24, five blocks are recorded by the append method. (2) Block (n + 2)
Data recording is performed at 30 by the update-in-place method. (3) After the block recorded in (1), five blocks are recorded by append method.

In these processes, data is recorded on the magnetic tape shown in FIG. 6 (a), so that the data has the form shown in FIG. 6 (b). When the buffer memory 12 is used in the form shown in FIG. 4 (a), data is stored in the buffer memory 12 in the form shown in FIG. 7 by these processes. First, in the data 201 to be recorded in the block (n + 10) 31, the block number (n + 10) 202 and an unpended flag to indicate that data recording by the update-in-place method is not performed are set in the flag area 203. It is stored in the form set in. Similarly, data for five blocks is stored in the buffer memory 12 until data to be recorded in the block (n + 14) 32.
Is stored in Next, the data 204 to be recorded in the block (n + 2) 30 has the block number 2
05 and update-in-place, which indicates that data is recorded by the update-in-place method
The flag is stored in the buffer memory 12 in a form set in the flag area 206. Subsequently, data to be recorded in the block (n + 15) 33 to the block (n + 19) 34 is stored in the buffer memory 12 from the block (n + 10) 31 to the block (n).
+14) Stored in the same manner as the data recorded in 32.

The data stored in the buffer memory 12 is
According to the processing shown in the figure, the data is transferred to the magnetic tape device 11 in the following order. First, the data to be recorded in the block (n + 10) 31 to the block (n + 14) 32 is transferred to the magnetic tape device 11 as it is because the append flag is set in the flag area. Record on magnetic tape. The data stored in the buffer memory 12 following these data is data to be recorded in the block (n + 2) 30. However, since the update-in-place flag is set in the flag area, the data is stored in the magnetic tape device 11. At this time, the data is not transferred at this time, and is stored in the buffer memory 12.
Continue from block (n + 15) 33 to block (n + 19) 34
Are recorded in the buffer memory 12, but these data are transferred to the magnetic tape device 11 as they are because the append flag is set in the flag area. Since these processes are performed continuously, 10 blocks of data from the data recorded in the block (n + 10) 31 to the data recorded in the block (n + 19) 32 are continuously transferred to the magnetic tape device 11. The magnetic tape device 11 positions the data at the recording start position 36 of the block (n + 10) 31 by a method not shown, and then continuously records these data on the magnetic tape.

After the transfer of the data to be recorded in the block to which the data recording by the append system is instructed and the recording on the magnetic tape are completed, the data to be recorded in the block (n + 2) 30 remaining in the buffer memory 12 is magnetically transferred. The data is transferred to the tape device 11. At this time, the magnetic tape device 11
Performs the positioning of the block (n + 2) 30 to the recording start position 35, and records this data in the position where the block (n + 2) 30 of the magnetic tape is recorded by the update-in-place method.

The operation of the magnetic tape by these processes is as shown in FIG. 6 (c). That is, positioning is performed at the recording start position 36 of the block (n + 10) 31 (37), and the block (n
After recording 10 blocks of data from (+10) 31 to block (n + 19) 34 (38), positioning is performed at the recording start position 35 of block (n + 2) 30 (39), and block (n +
2) Record 30 (40).

As described above, the flag for identifying the block for performing the data recording by the update-in-place method and the block for performing the data recording by the append method are added to the data to be recorded in each block, and the recording is performed by the update-in-place method. The number of positioning to the recording start position on the magnetic tape is reduced by controlling the recording of the block to be performed on the magnetic tape to be performed after all the blocks for performing the data recording by the append method are recorded on the magnetic tape. Recording time can be reduced.

FIG. 8 shows a case in which the buffer memory 12 is divided into two areas in advance and the control is performed to obtain the same effect as in the above embodiment. An area 65 is used as an area for storing data of a block for performing data recording by the update-in-place method, and an area 66 is used for storing data of a block for performing data recording of the append method. The buffer memory 12 performs the processing shown in FIG.
This corresponds to the process of step 2 in FIG. Upon receiving the data transferred from the host computer 13 (step 81), the buffer memory 12 first checks whether the data is to be recorded in the update-in-place method or to be recorded in the append method. (Step 82). If the data is to be recorded in the block in which data is recorded by the update-in-place method, the data is stored in the data area 65 in FIG. 8 where data is recorded by the update-in-place method (step 83). ). Further, the data of the block for performing the data recording by the append system is stored in the data area 66 for performing the data recording by the append system in FIG. These processes are performed for all blocks transferred by the host computer 13 (step 85). The data transfer from the buffer memory 12 to the magnetic tape device 11 is first performed from the data stored in the data area 66 where data is recorded by the append method. After transferring all the data stored in the area 66 to the magnetic tape device 11, that is, recording the data on the magnetic tape, the data stored in the data area where data is to be recorded by the update-in-place method 65 is magnetically transferred. The data is transferred to the tape device 11.

In the above description, the transfer of the data in the area where the data recording by the update-in-place method is performed to the magnetic tape device is performed after the transfer of the data area where the data recording in the append method is completed. The object can also be achieved by recording once just before the use of the magnetic tape attached to the magnetic tape device is finished. In this case, the data stored in the buffer memory can be read if required by the host computer. In addition, when the magnetic tape is mounted on the magnetic tape device, the data area where the data of the block recorded on the magnetic tape by the update-in-place method is recorded by the update-in-place method of the buffer memory. To the host computer and update-in
It is possible to adopt a configuration in which data transfer to and from a block on which data recording is performed by the place method is performed to and from a buffer memory without actually accessing the magnetic tape.

Next, an embodiment in which the control method of the magnetic tape device and the buffer memory of the present invention is applied to a so-called helical scan type magnetic tape device will be described.

The magnetic tape device of this embodiment uses a DAT as a magnetic tape.
(Digital Audio Tape Recorder) A magnetic tape used in a digital audio tape recorder is used.

The magnetic tape device of this embodiment includes a rotary cylinder 301, read heads 311a and 311b, and write heads 312a and 312 shown in FIG.
b, R / W (read / write) circuit 313, verify circuit 314,
Servo circuit 315, cylinder motor 316, capstan motor
317, reel motor 318, DAT signal processing circuit 319, serve code control circuit 320, drive control circuit 321, DAT code decoding circuit 3
22, a memory control circuit 323, a layered ECC (layered error correction code) circuit 324, a buffer memory 325, a system control circuit 326, a SCSI (small computer system interface) 327, and a mechanical drive circuit 328. The read heads 311a and 311b and the write heads 312a and 312b are attached to the rotary cylinder 310 at azimuth angles different from each other by ± 20 degrees.

The format of the magnetic tape 329 used in the magnetic tape device of the present invention is based on the DAT recording format. Magnetic tape 329 is 6 degrees with respect to rotating cylinder 310
Tilt at a 22 minute lead angle, wound 90 degrees
Drive at 8.15mm / sec. At this time, the rotating cylinder 310
By running the magnetic tape 329 rotating at rpm,
The read heads 311a, 311b and the write heads 312a, 312b scan obliquely on the magnetic tape 329, and the recording operation of the write heads 312a, 312b causes the read operation on the magnetic tape 329.
Tracks are formed as shown in FIG.

In FIG. 14, reference numeral 331 denotes a track recorded by the write head 312a, and 322 denotes a track recorded by the write head 312b. As described above, gapless azimuth recording is performed by recording the adjacent tracks so that the azimuth angles are different, and by overlapping with the part of the immediately preceding track. The track pitch P is 13.6 μm, the track length L is 23.5 mm, and the recording width W is 2.61 mm.

FIG. 15 shows the structure of the signal recorded on each track. This track format was standardized at the DAT roundtable.

As shown in FIG. 15, the track is divided into a plurality of recording areas, and various signals are recorded in the divided areas.

The track is composed of a PCM signal area (PCM) 343 of 128 data blocks arranged in the center of the magnetic tape 329 and ATF signal (automatic track finding signal, tracking reference signal) areas (ATF-
1, ATF-2) 342, 344, and sub-code areas (SUB-1, SUB-
2) It is composed of 341 and 345.

In DAT, the PCM (pulse code modulation) signal area 343 contains audio data converted to PCM digital data,
Data to which an error correction code is added is recorded. In the magnetic tape device of this embodiment, data obtained by adding an error correction code to digital data used by a computer or the like is recorded in the PCM signal area 343.

In the subcode areas 341 and 345, search information for searching for a specific position of data on the magnetic tape 329 is recorded.

In the ATF signal areas 342 and 344, ATF signals for tracking control (the magnetic head is caused to travel on an inclined track having a corresponding azimuth angle during reproduction) are recorded.

In DAT, signals recorded on the recording tape 329 are handled in units called data blocks. For example PCM
The signal area 343 is composed of 128 data blocks. PC
FIG. 16 shows the configuration of the data block in the M signal area 343. One data block consists of 32 symbols (one symbol is 8b
Itt) includes, in the main data 355, a synchronization signal (SYNC) 351, a main ID 352, a block address 353, and a parity 3 for detecting an error in the main ID 352 and the block address 353.
One symbol of 54 is added to each, making up a total of 36 symbols.

The block configuration of the PCM signal area 343 in FIG.
As shown in FIG. The PCM signal area 343 is composed of a total of 128 data blocks, and is composed of data composed of a SYNC area 356, a main ID area 357, a block address area 358, a parity area 359, main data 355 of a 128 data block, and an error correction code area 360. Is done. In the DAT track format, the size of the data area excluding the error correction code, in other words, the capacity of the user to record data is 2880 bytes per track.

In the DAT, in order to perform data recording by the update-in-place method, recording and reproduction of data on a magnetic tape are performed in units of a group of a plurality of tracks. FIG. 18 shows the group format.

One group is composed of 32 frames (two tracks are called one frame, meaning 64 tracks). From frame 381 with frame number -31 to frame 3 with -1
Three frames up to 28 and a frame 385 having a frame number of 28 are defined as gaps between groups. Therefore, 28 frames from the frame 383 with the frame number 0 to the 31st frame 384 with the frame number 327
Each frame is an area for recording data. The frame numbers in the group are numbered from “−3” to “28” as shown in FIG. 18, with the frame number of the first frame of the data recording area being “0”. This frame number is recorded in the above-described subcode areas 341 and 345 together with a group number described later, and is used for search.

FIG. 19 shows the configuration of an area for recording group data. As described with reference to FIG. 18, this area includes 28 frames from frame 383 of frame number 0 to frame 384 of frame number 27. In DAT, data recorded on one track is 2880 bytes. Therefore, it becomes 161280 bytes in 28 frames.

Normally, an integer multiple of 256 bytes is used as a logical block of a computer. Therefore, of the data of 28 frames, 131072 bytes (256 × 512 bytes) are set as a data area (391 in the figure) that can be used by the user.

Of the remaining 30208 bytes, 4736 bytes are used as the system area (392 in the figure) used by the magnetic tape device itself.
Bytes for error correction using Reed-Solomon code
Used for C3 parity (393 in the figure). In the system area 392, it is impossible for the user to directly record and reproduce arbitrary data, and information for the magnetic tape device to manage the magnetic tape 329 is recorded. The remaining 8 bytes are unused.

The C3 parity 393 for error correction is added to data in both the data area 391 and the system area 392 to correct data errors along the running direction of the magnetic tape 329, and the DAT
In addition to the error correction by the error correction code used in the track No. 1, the data can be corrected even if a burst error of eight consecutive tracks occurs.

Each group is assigned a group number and a magnetic tape
329 are managed in units of this group. This group number is recorded in the subcode areas 341 and 345 described above.

In the magnetic tape device according to the present embodiment, even when data is recorded by the append method, recording is performed on the magnetic tape in units of groups, similarly to the data recording by the update-in-place method described above. This is described earlier
This is to improve data reliability by adding C3 parity. However, when data is recorded by the append method, the gap in FIG. 18 is not recorded. This is because the group that has been recorded once is not rewritten and is not necessary. That is, the group format when data is recorded by the append system is composed of only 28 frames from a frame 383 having a frame number of 0 to a frame 384 having a frame number of 327. Therefore, the configuration of the area for recording data in the group format when data is recorded by the append method is the same as that in the group format when data is recorded by the update-in-place method, and is shown in FIG. It takes shape.

FIG. 20 shows the configuration of the system area 392. The system area 392 has a size of 4736 bytes. Of these, the top 409
Six bytes are used for the record ID list area 394. In the record ID list area 394, attribute information of all records recorded in the group is recorded. The record is the minimum unit of data recorded on the magnetic tape 329. The subsequent 512-byte area is a reserved area 395. Reserved area 395
Is an area reserved for future expansion of functions. The last 128-byte area is used as a group ID 396, and the group attribute information and the like are recorded.

FIG. 21 shows a tape layout in the magnetic tape device of this embodiment. A load / unload area 401 is recorded at the head of the magnetic tape. Load / unload area 401
Is an area where the magnetic tape is mounted on the magnetic tape device and the magnetic tape is loaded on the rotating cylinder. During the operation of loading or unloading the magnetic tape from the rotating cylinder, the possibility of damaging the magnetic tape is high. Therefore, the loading / unloading of the magnetic tape to / from the rotating cylinder is always performed at a predetermined position, here, the loading / unloading area 401, thereby ensuring the reliability of the area where the user records data. The subsequent lead-in area 402 is an area for recording information necessary for the magnetic tape device to manage the magnetic tape, and includes a preamble 405, a header 406, a reference 407, and a postamble.
408. The header 406 records fixed information on the magnetic tape, for example, information on the date and time when the use of the magnetic tape started, and information on the format of the magnetic tape. The reference 407 records information on data recorded on the magnetic tape. The data area 403 is an area where the user records data. As described above, recording is performed here in units of groups. In the case of performing data recording by the update-in-place method, the data is recorded in a group format having a gap before and after the group shown in FIG. 18 (hereinafter, referred to as group format 0) and in an append method. Is recorded in a group format (hereinafter, referred to as group format 1) in which the front and rear gaps are removed from the group format shown in FIG. Which group format is recorded in the data area 403 is recorded in the reference 407. Therefore, by referring to the reference 407, it is possible to determine in which group format a group having a certain group number is recorded, in other words, whether data recording by the update-in-place method is possible or not. It is. The EOI 404 is a group indicating the end position of the recorded valid data, and indicates that no valid data is recorded thereafter. When additional data is recorded, recording is performed from the start position of the already recorded EOI 404, that is, data is recorded following the last part of the already recorded data, and a new EOI 404 is added after the recorded data. Record This allows EO
I404 always indicates the end of valid data.

Also in this embodiment, the buffer memory 325 is used in the form shown in FIG. That is, to the data of the block sent from the host computer through SCSI327,
The block is stored in the buffer memory 325 with a flag indicating whether the block is a block for recording in the update-in-place system or a block for data recording in the append system. Therefore,
The process of transferring data from the host computer to the buffer memory 325 is as shown in FIG. 3B, and the process of transferring data stored in the buffer memory to the magnetic tape is also as shown in FIG.

In this embodiment, data transferred from the host computer to the magnetic tape via the SCSI 327 is transferred in units of blocks. In the magnetic tape device of this embodiment, this block is recorded on a magnetic tape as a record in the above-described tape format. Therefore, a plurality of blocks are recorded in one group.

In the present embodiment, processing for recording data on a magnetic tape will be described.

It is assumed that a host computer connected to a magnetic tape device records data in a group having a group number n. The host computer transmits a write command for recording data in the block n via the SCSI 327. Prior to this, the host computer was SCSI327
Check that the bus is not being used by another device, and if not, acquire the usage right. Next, the SCSI ID given to the magnetic tape device of the present invention is transmitted to the SCSI327 bus. The system control circuit 326 is connected to the SCSI 327 bus via the SCSI 327, and the same SCS is given to itself.
When it is detected that the ID of I is output, a command from the host computer, here, a write command is received.

Upon receiving the write command, the system control circuit 326 instructs the drive control circuit 321 to perform a “reproduction mode” in order to search for a group n in which to record data, and the cylinder motor 316 and the capstan motor 317 via the servo circuit 315. , Respectively. A signal read by the read heads 311a and 311b is converted into a DAT signal processing circuit 319.
The data read out from the sub-code areas 341 and 345 are transmitted to the sub-code control circuit 20, where an error check is performed.
And reads the current group number of the magnetic tape 329. If the current group number is smaller than the target group number n, the search is performed in the direction in which the group number increases (forward search), and if it is larger, the search is performed in the direction in which the group number decreases (reverse search). During the search, the host computer waits for data.
This would occupy 327 buses. Therefore, during this time, the devices connected to the other SCSI327 bus cannot use the SCSI327 bus, and the usage efficiency of the SCSI327 bus is reduced. To avoid this, the system control circuit 326 sends a save pointer message and a disconnect message for instructing the disconnection of the SCSI327 bus to the host computer before performing the search. Upon receiving this message, the host computer stores the memory address of the host computer storing the data to be recorded on the magnetic tape 329 in a predetermined memory, and temporarily stops using the SCSI327 bus. On the other hand, after transmitting this message, the system control circuit 326 once relinquishes the bus use right of the SCSI 327. Therefore, in this state, the SCSI327 bus becomes unused, and other devices can use the SCSI327 bus. As described above, in the magnetic tape device, the search is performed once with the SCSI327 bus disconnected.

In the search, the magnetic tape 329 is run at 200 times the normal recording / reproducing speed, and the number of rotations of the rotary cylinder 310 is increased by the magnetic tape 329, the read heads 311a, 311b, and the write head 312a attached to the rotary cylinder 310. , 312b is controlled to be the same as the normal recording / reproducing speed, the data recorded in the subcode areas 341 and 345 are read, and the target group is detected.

After determining the direction of the search, the microcomputer 1 notifies the servo circuit 315 via the drive control circuit 321 whether the search is a forward search or a reverse search. The servo circuit 315 drives the reel motor 318 in order to cause the magnetic tape 329 to travel in the designated direction at a magnification of 200 times. Servo circuit 3
Numeral 15 controls the sum of the reel pulses taken out from the supply-side reel and the take-up side reel of the magnetic tape 329 to be a constant value. At the same time, the rotation of the rotary cylinder 310 is controlled to be 3000 rpm in the case of the forward search and 1000 rpm in the case of the reverse search. At this time, the read heads 311a and 311b attached to the rotary cylinder 310 cross a plurality of tracks on the magnetic tape 329.
Due to the read head azimuth, the signal of the same azimuth track has a large output and the signal of the different azimuth track has a small output, so by counting the number of large output signals, the number of tracks traversed You can know. Therefore, the reel motor 318 is controlled so that this number becomes constant.

In this state, the signal output from the read heads 311a and 311b is a part of the track, and the DAT signal processing circuit 319 determines whether or not two consecutive blocks of the subcode areas 341 and 345 provided in the track are read without error. Via the sub-code control circuit 320. The data of the subcode areas 341 and 345 are configured so that necessary information can be obtained by performing continuous two-block reading. That is, when two consecutive blocks are correctly read, it is possible to know the group number including the track.

The subcode control circuit 320 sends the data of the blocks of the subcode areas 341 and 345 that have been correctly read out to the system control circuit 326, and the group numbers included in the data recorded in the subcode areas are set as the target group numbers n and n. Compare. If matched, microcomputer 1
Indicates the “stop mode” to the servo control circuit 315 via the drive control circuit 321, temporarily stops the reel motor 318, returns the rotary cylinder 310 to 2000 rpm, which is the speed at which normal data is reproduced, and then sets the group number n The magnetic tape 329 is checked for the group number and the frame number included in the data recorded in the subcode areas 341 and 345 until the first track of the reel motor 318 can be reproduced.
Use to move.

Thereafter, the drive control circuit 321 and the servo control circuit 315 are set to the “reproduction mode”, the read signal is processed by the DAT signal processing circuit 319, and the data recorded in the subcode areas 341 and 345 are transmitted to the subcode control circuit 320. The data transmitted and recorded in the PCM signal area 343 is a DAT code decoding circuit.
Send to 322. The subcode control circuit 320 has the subcode 34
By analyzing the data recorded in 1,345,
DAT from frame 383 with frame number 0
The code decoding circuit 322 is activated.

The DAT code decoding circuit 322 starts operation with the signal from the subcode control circuit 320, and in the playback mode, decodes the received signal and stores the data for each track in the buffer memory 325 via the memory control circuit 323. I do. When data up to a frame 384 having a frame number of 327 is stored in the buffer memory 325, the system control circuit 326
Is a memory control circuit 323, a layered ECC circuit 324
Is used to perform apology detection and correction using the C3 parity 393. The result of the apology correction is stored in the buffer memory 325 again.

After reading the data of the group n into the buffer memory 325, the system control circuit 326 performs reselection of the SCSI327 bus to receive data to be recorded from the host computer, and sends out a reconnect message. Upon receiving this, the host computer reconnects the SCSI327 bus and sends data to the SCSI327 bus. The system control circuit 326 receives this data via the SCSI 327, and from the data of the group n read from the magnetic tape 329 to the buffer memory 32 from the position where the data is to be recorded.
Store in 5. When receiving these data, the system control circuit 326 can know the group number of the group that records the data from the block number of the data. Therefore, by referring to the reference 407, it is possible to know whether the data of the block is data to be recorded by the update-in-place method or data to be recorded by the append method. In this embodiment, the difference between these two methods is the difference in the group format when data is recorded. Blocks to be recorded by the update-in-place method are recorded in group format 0, and blocks to be recorded by the append method are recorded in group format 1. The system control circuit 326 stores the received block in the data buffer memory 325,
As shown in FIG. 4 (a), the update-in-place flag stores the append flag in the flag area for storing the data of the block. When the reception of the data of the specified block is completed, check whether a parity error has occurred on the SCSI327 bus during the data transfer by the SCSI327, and if the transfer has been performed correctly, the good status is reported to the host computer. And sends a command complete message to end the command. If a parity error has occurred, a check condition is set in the status, and the content of the error is set in the sense data. Of course, when a sense status command is received from the host computer, this data is sent out to notify the contents of the error.

The system control circuit 326 uses the layered ECC circuit 324 for the data stored in the buffer memory 325.
The C3 parity 393 is added and stored in the buffer memory 325. The data is transmitted from the memory controller circuit 323 to the DAT encoding / decoding circuit 322, the error correction parity determined in the DAT track is added, and the data is output to the DAT signal processing circuit 319 as serial data. Upon receiving this data, the DAT signal processing circuit 319 performs 8-10 conversion of the data in accordance with the data format in the track and inputs the data to the verify circuit 314, and at the same time, via the R / W circuit 313, the write head 31.
Signals are recorded on the magnetic tape 329 by 2a and 312b. At this time, the read heads 311a and 311b read the data recorded by the write heads 312a and 312b, and input the data to the verify circuit 314 via the DAT signal processing circuit 319. The verify circuit 314 compares the recorded signal with the read signal to check whether they match. The number of signals that do not match for each square track is transmitted to the system control circuit 326. System control circuit 326
Collects the number of unmatched signals for one group and checks whether the number is in a range where error correction is possible. For this determination, a threshold that can be set by the user is used, and if the signals do not match within N% of the error correction capability, the processing is continued assuming that the signal has been correctly recorded.

If a signal mismatch is detected that exceeds this threshold hold, the group is not recorded correctly and will not be used in the future, but will instead be recorded in succession with the same group. Therefore, when a group having the same group number is successively read at the time of data reading, the previously read group is invalid and skipped.

In accordance with FIG. 5, data recording on the magnetic tape 329 is performed from data in the block in which the append flag is set in the flag area in the buffer memory 325.

In any case, according to the present embodiment, the update
Enables the magnetic tape device to identify on the buffer memory the data of the block for which data recording is performed by the in-place method and the data of the block for which data recording is performed by the append method, and the data of the block for which data recording is performed by the append method Since the recording is performed prior to the data recording by the update-in-place method, the recording of the block for performing the data recording by the append method on the magnetic tape can be performed by positioning to the recording start position once, By reducing the number of times of positioning to the recording start position, it is possible to shorten the data recording time on the magnetic tape.

〔The invention's effect〕

According to the control method of the magnetic tape device and the buffer memory connected thereto according to the present invention, it is possible to rewrite data on a magnetic tape in a magnetic tape device and a buffer memory having a function of rewriting already recorded data. Even if the area and the area that cannot be rewritten are mixed, the data to be recorded in each area is separately stored in the buffer memory, and the recording of the data in the area to be rewritten is completed in the area in which the data is not rewritten. After that, the number of times of positioning to the recording start position on the magnetic tape can be reduced, so that the time required for data recording can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of processing of data recording on a magnetic tape device in a control method of a magnetic tape device and a buffer memory. FIG. 2 is a diagram showing an example of the configuration of a magnetic tape device in a control method of a magnetic tape device and a buffer memory connected thereto, and FIG. 3 shows a flow of data storage processing in a buffer memory in an embodiment using flags. FIG. 4 is a diagram showing a configuration of a buffer memory;
FIG. 5 is a diagram showing the flow of processing of data transfer from the buffer memory to the magnetic tape, and FIG. 6 shows an example of a tape format in the magnetic tape device and the magnetic tape device using the buffer memory control method of the present invention. FIG. 7 is a diagram showing the contents of the buffer memory in the embodiment using the flag. FIG. 8 is a diagram showing the configuration of the buffer memory in the embodiment in which the buffer memory is divided into two areas.
FIG. 10 is a diagram showing a flow of processing for storing data in the buffer memory in an embodiment in which the buffer memory is divided into two areas, FIG. 10 is a diagram for explaining a conventional example, and FIG. 11 is a method of using the buffer memory. FIG. 12 is a diagram for explaining a method of using a buffer memory in a conventional example. FIG. 13 is a diagram showing a configuration of a magnetic tape device and a buffer memory in an embodiment in which the control method of the magnetic tape and the buffer memory of the present invention is applied to a helical scan type magnetic tape device. FIG. 14 is a diagram showing a recording method on a magnetic tape in a helical scan type magnetic tape device, FIG. 15 is a diagram showing a configuration of a track in a DAT, FIG. 16 is a diagram showing a configuration of a data block in a DAT, FIG. 17 is a diagram showing the configuration of a data recording area in the DAT, FIG. 18 is a diagram showing the configuration of a group in the embodiment described in FIG. 13, FIG. 19 is a diagram showing the configuration of a data recording area of the group, FIG. FIG. 20 is a diagram showing the configuration of the system area of the group, and FIG. 21 is a diagram showing the tape format of the magnetic tape used by the magnetic tape device of the embodiment shown in FIG. 2. Data recording and update using append function
A step of adding identification information to the data recording by the in-place function; 3, a step of recording data by the append function; 4, a step of recording data by the update-in-place function; 11: a magnetic tape device , 12: Buffer memory, 13: Host computer, 61: Flag storage area, 63: Data storage area, 66: Flag storage area, 325: Buffer memory, 327: SCSI, 402: Lead-in area , 403 ... data area, 407 ... reference.

Claims (3)

(57) [Claims] 1. A function of rewriting data already recorded on a magnetic tape (update-in-place function)
A magnetic tape device having a function of recording data from an end position of data already recorded on the magnetic tape (append function), and a buffer connected to the magnetic tape device and temporarily storing data to be recorded on the magnetic tape In a memory and an electronic computer system connected to the buffer memory and using the magnetic tape device as an external storage device, data transferred from the electronic computer system to the buffer memory for recording on a magnetic tape,
Whether the data is data to be recorded on the magnetic tape by the update-in-place function or data to be recorded on the magnetic tape by the append function is stored in a buffer memory together with information indicating whether the data is data to be recorded on the magnetic tape. When the data to be recorded on the magnetic tape is taken out from the buffer memory, the information is examined.After all the data to be recorded on the magnetic tape are recorded on the magnetic tape by the append function, the data to be recorded on the magnetic tape by the update-in-place function is retrieved. A control method for a magnetic tape device and a buffer memory, characterized in that recording is performed on a magnetic tape. 2. The control method of a magnetic tape device and a buffer memory according to claim 1, wherein the data transferred from said electronic computer system to said buffer memory for recording on said magnetic tape is updated in place. A function to store the data in the buffer memory together with a flag indicating whether the data is to be recorded on the magnetic tape by the function or the data to be recorded on the magnetic tape by the append function, and the magnetic tape device sets the flag when extracting the data from the buffer memory. A magnetic tape characterized in that, after checking and recording all the data to be recorded on the magnetic tape by the append function, the data to be recorded on the magnetic tape by the update-in-place function is recorded on the magnetic tape Device and buffer memory control method. 3. A control method for a magnetic tape device and a buffer memory according to claim 1, wherein said buffer memory has a first area for storing data to be recorded on a magnetic tape by an update-in-place function, and an appending method. And a second area for storing data to be recorded on the magnetic tape by the function. The magnetic tape device records the data stored in the second area on the magnetic tape and then stores the data in the first area. A magnetic tape device and a buffer memory, wherein the recorded data is recorded on a magnetic tape.