Access control device, access control method, and program

Abstract

To provide an access control device that more efficiently accesses information on one magnetic tape that stores one or more blocks as one unit of data. [Solution] The system includes a control means for reading information from a magnetic tape that stores a collection of one or more block units as one unit of data. The control means waits for the read process of data for data numbers other than one specified one of the data numbers based on a read access command that includes the data numbers of one or more data. The control means starts the read process of data for one specified data number from the data numbers, determines whether there are one or more block units corresponding to the data with that data number, and reads the data in block units in order. After reading of all block units included in the data with the specified data number is completed, one of the other waiting data numbers is identified and the read process is repeated in the same manner.

Description

[Technical Field]

[0001] The present disclosure relates to an access control device, an access control method, and a program. [Background technology]

[0002] LTFS (Linear Tape File System) is a technology for reading and writing information from and to magnetic tape. When reading and writing information using LTFS, users can intuitively write and read information on a file-by-file basis, in the same way as they write and read information to and from a storage device such as a hard disk while visually checking a terminal such as a PC.

[0003] For example, Patent Document 1 discloses a technique aimed at reducing the waiting time for accessing a magnetic tape in a system that manages data stored on the magnetic tape using an LTFS file system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-136752 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology described in Patent Document 1 aims to reduce the waiting time for accessing magnetic tapes in a library device that has multiple drives and uses the multiple drives to perform data synchronization processing between at least two magnetic tapes among multiple recording media.

[0006] There is a demand for a technology that allows for more efficient access to information on a magnetic tape that stores data in units of one or more blocks.

[0007] An object of the present disclosure is to provide an access control device, an access control method, and a program that solve the above-mentioned problems. [Means for solving the problem]

[0008] An access control device according to one aspect of the present disclosure includes a control means for reading information from a magnetic tape that stores a group of one or more block units as one unit of data, and the control means, based on a read access command including the data numbers of one or more of the data, waits for a read process for data of a data number other than a specified one of the data numbers, starts a read process for data of a specified one of the data numbers, determines whether or not there are one or more block units corresponding to the data of the data number, reads the data in the block units in order, and after reading of all block units included in the data of the specified one data number is completed, identifies one of the other waiting data numbers, starts a read process for data of the specified one data number, determines whether or not there are one or more block units corresponding to the data of the data number, and repeats the read process in the block units in order.

[0009] In an access control method according to one aspect of the present disclosure, a control means for accessing information on a magnetic tape that stores a group of one or more block units as one unit of data waits for access processing of data of a data number other than a specified one of the data numbers based on an access command including the data numbers of one or more of the data, starts access processing of data of a specified one of the data numbers, determines whether or not there are one or more block units corresponding to the data of that data number, accesses the data in block units in order, and after accessing all block units included in the data of the specified one data number is completed, identifies one of the other waiting data numbers, starts access processing of data of the specified one data number, determines whether or not there are one or more block units corresponding to the data of that data number, and repeats the access processing in block units in order.

[0010] A program according to one aspect of the present disclosure causes a computer having a control means for accessing information on a magnetic tape that stores a collection of one or more block units as one unit of data to execute a process of waiting for access processing of data of a data number other than a specified one of the data numbers based on an access command including the data numbers of one or more of the data, starting access processing of data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, accessing the data in the block units in order, and after accessing all block units included in the data of the specified one data number is completed, identifying one of the other waiting data numbers, starting access processing of data of the specified one data number, determining whether or not there are one or more block units corresponding to the data of the specified data number, and repeating the access processing in the block units in order. [Effects of the Invention]

[0011] According to the above aspect, a group of one or more block units This allows for more efficient access to information stored on a single magnetic tape as a unit of data. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a magnetic tape system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a hardware configuration diagram of an access control device according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a diagram illustrating a structure of data stored on a magnetic tape according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a first diagram illustrating a processing flow of an access control device according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram showing a processing flow of a related access control device. [Figure 6] This is a diagram showing two different access control processes in chronological order. [Figure 7] FIG. 10 is a functional block diagram of an access control device according to another embodiment. [Figure 8] FIG. 10 is a diagram showing a processing flow of an access control device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Each embodiment will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a magnetic tape system according to an embodiment of the present disclosure. The magnetic tape system 1 of the present disclosure includes a magnetic tape drive 100 and a Linear Tape File System (LTFS) 200. The magnetic tape drive 100 and the LTFS 200 are communicatively connected.

[0014] The magnetic tape drive 100 comprises an access control device 10, a magnetic tape 20, and a head 30. The magnetic tape 20 stores data. The access control device 10 controls access to the magnetic tape 20. The head 30 moves to an access position where it reads and writes data from and to the magnetic tape 20 under the control of the access control device 10. The access control device 10 performs the functions of an exclusive control unit 11 by executing an exclusive control program.

[0015] Here, the highly convenient LTFS is used when handling the magnetic tape 20 in the magnetic tape drive 100. LTFS is a file system that makes it possible to handle data on the magnetic tape 20 on a file-by-file basis. While dedicated software was previously required to operate the magnetic tape 20, LTFS makes it possible to use the magnetic tape 20 with simple operations, just like data on a hard disk drive.

[0016] When reading data, LTFS provides the magnetic tape drive 100 with the target data number, data location (recording position on magnetic tape 20), and data capacity (number of data blocks) as parameters of the access command, reads the data in blocks, and sends the data in one file to a higher-level device, etc.

[0017] FIG. 2 is a hardware configuration diagram of an access control device according to an embodiment of the present disclosure. As shown in FIG. 2, the access control device 10 may be a computer equipped with hardware such as a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a storage device 104, a communication module 105, and an input device 106.

[0018] FIG. 3 is a diagram showing the structure of data stored on a magnetic tape according to an embodiment of the present disclosure. As shown in Figure 3, the magnetic tape 20 stores one or more blocks as one unit of data. Specifically, Figure 3 shows n pieces of data, Data 1, Data 2, Data 3, ... Data n-1, Data n, recorded on the magnetic tape 20. Data 1 shows a state in which information in three blocks, Block 1-1, Block 1-2, and Block 1-3, is recorded. Data 2 shows a state in which information in two blocks, Block 2-1 and Block 2-2, is recorded. Data 3 shows a state in which information in five blocks, Block 3-1 to Block 3-5, is recorded. Data n-1 shows a state in which information is recorded in five blocks, Block (n-1)-1 to Block (n-1)-5, is recorded. Data n-1 shows a state in which information is recorded in five blocks, Block n-1 to Block n-5.

[0019] When the LTFS 200 receives an access command from a higher-level device, it transfers the access command to the access control device 10. As described above, the access command may include a data number and a block number included in the data indicated by the data number.

[0020] The exclusive control unit 11 of the access control device 10 identifies one data number based on a read access command including the data numbers of one or more data, and puts the read process of data other than the identified data number on hold under exclusive control. The exclusive control unit 11 starts the read process of the data of the identified data number from among the data numbers, determines whether there are one or more block units corresponding to the data of the identified data number, and reads the data in block units in order. After reading all block units included in the data of the identified data number is completed, the exclusive control unit 11 identifies one of the other waiting data numbers, starts the read process of the data of the identified data number, determines whether there are one or more block units corresponding to the data of the identified data number, and repeats the read process in block units in order.

[0021] Here, the magnetic tape 20 is made up of multiple tracks, and data recorded on the tracks is recorded in units of multiple blocks. The data size of these blocks is uniform. The operation of winding or rewinding the magnetic tape 20 and moving the head 30 to align it with the data block reading or writing start position is called cueing.

[0022] FIG. 4 is a first diagram illustrating a processing flow of the access control device according to an embodiment of the present disclosure. Next, the processing flow of the access control device 10 will be described.

[0023] First, the LTFS 200 obtains an access command from a higher-level device. The access command may include a data number. For example, suppose that the access command includes data n (n: number). Let n=1, 2, 3. In other words, suppose that the access command commands access to data 1, data 2, and data 3. Furthermore, suppose that this access command includes a read command for each data. The LTFS 200 outputs the access command to the access control device 10.

[0024] The exclusive control unit 11 of the access control device 10 receives an access command. In response, the exclusive control unit 11 starts a data read process (read-out process) (step S101). The exclusive control unit 11 identifies data 1 with the smallest value of n among the data n numbers included in the access command, and determines that the other data 2 and data 3 should be exclusively controlled. The exclusive control unit 11 records information about data 2 and data 3 that have been determined to be exclusively controlled in a storage unit (step S102).

[0025] The exclusive control unit 11 controls the movement (locates) of the head 30 relative to the magnetic tape 20 based on the recording position of data n (n=1) identified for access control (data read) (step S103). The recording position of data n may be stored in advance in the storage device 104 for each data n. The exclusive control unit 11 identifies block ns included in data n (n=1) identified for access control (data read) (step S104). For example, a block with block number s included in data n will be referred to as block ns. Information about block ns may be included in the access command, or may be stored in advance in the storage device 104 by the access control device 10 as information about blocks included in data n. Assume that block numbers s included in data 1 are three blocks with s=1, 2, and 3. In this case, the exclusive control unit 11 identifies block 1-1 of block number 1 included in data ns. In other words, the exclusive control unit 11 identifies block ns with the smallest block number s among the blocks included in data n identified for access control.

[0026] The exclusive control unit 11 controls the head 30 to move to the read position of block 1-1 on the magnetic tape 20 so that the information of the identified block 1-1 can be read. The read position of each block number may also be stored in advance in the storage device 104, or information about the read position may be included in the access command. This causes the head 30 to move to the read position of block 1-1 on the magnetic tape 20. The exclusive control unit 11 instructs the head 30 to read block 1-1, and the information of block 1-1 is read from the head 30 (step S105). The exclusive control unit 11 outputs the information of block 1-1 to the LTFS 200.

[0027] The exclusive control unit 11 then calculates a new block number s = s + 1 and determines whether the new block ns is included in data n (step S106). That is, the exclusive control unit 11 determines whether block number 1-2 is included in data 1 based on the new block number s = 1 + 1 = 2. Because block number 1-2 is included in data 1, the exclusive control unit 11 controls the head 30 to move to the read position of block 1-2 on the magnetic tape 20 so that the information of the identified block 1-2 can be read. As a result, the head 30 moves to the read position of block 1-2 on the magnetic tape 20. The exclusive control unit 11 instructs the head 30 to read block 1-2, and the information of block 1-2 is read from the head 30. The exclusive control unit 11 outputs the information of block 1-2 to the LTFS 200. The exclusive control unit 11 similarly determines whether the new block number s is included in data n, obtains information of block 1-3, and outputs the information of block 1-3 to the LTFS 200.

[0028] If there is no next new block number included in data n in step S106, the exclusive control unit 11 sets s to 1 and identifies the next highest new data number n from the storage unit recorded in the exclusive control of step S102 (step S107). That is, the exclusive control unit 11 identifies the next new data number 2. The exclusive control unit 11 may delete the identified data number 2 from the storage unit stored by the exclusive control. The exclusive control unit 11 determines whether the new data number n is larger than the largest number D among the data numbers identified by the access instruction (step S108). If the new data number n is larger than the largest number D among the data numbers identified by the access instruction, the exclusive control unit 11 ends the data read. If the new data number n is smaller than the largest number D among the data numbers identified by the access instruction, the exclusive control unit 11 identifies the data and starts the process of step S103. That is, the exclusive control unit 11 similarly reads the blocks of block 2-s included in data 2, starting from block 2-1.

[0029] FIG. 5 is a diagram showing a processing flow of the related access control device. Next, the processing flow of the related access control device will be described. The associated access control device starts reading the first data n, which is the smallest data n included in the access command (step S61), and then controls (cues) the head position relative to the magnetic tape 20 so that the information of data n can be read (step S62). After controlling the movement of the head position, the associated access control device performs a block read, i.e., reads the information of the block (step S63).

[0030] In this block read, the associated access control device sets block number s=1 and determines whether block ns is included in data n (step S631). If block ns is included, it controls movement of head 30 to the position of block ns (step S632), reads information about block ns (step S633), and ends the block read process. In other words, even if data n includes multiple blocks with block ns, once the associated access control device has finished reading information about one block ns, it temporarily stops reading information about other blocks included in that data n.

[0031] The associated access control device then identifies the next new data number n (n=n+1) and determines whether the new data number n is larger than the largest number D of the data numbers identified by the access command (n>D) (step S64). If the new data number n is smaller than the largest number D of the data numbers identified by the access command, the access control device reads information of one block number in the data number n and ends the process, similar to the process of step S63 (steps S631 to S633). In other words, the associated access control device reads information of the block of one block number in the data of one data number and stops the read process. The associated access control device then performs similar read processes on the data of the other data numbers included in the access command.

[0032] The associated access control device transfers control to processing the first data n with the smallest n among the data n included in the access command, sets block number s = s + 1, and determines whether the calculated block number s is greater than the maximum number of blocks B included in the data (s > B) (step S65). If the calculated block number s is smaller than the maximum number of blocks B included in the data, the associated access control device reads information on the next block number in the data number n and ends the process, similar to the process in step S63 (steps S631 to S633). If the calculated block number s is greater than the maximum number of blocks B included in the data, the associated access control device ends the process.

[0033] According to the processing of such a related access control device, when reading from a plurality of data included in an access command, the blocks are read one by one for each data in turn, and when information for one block has been read from all the data, the processing of reading information for the next block from all the data in turn is repeated. Therefore, in the processing of the related access control device, when information for one block of certain data is read, the head moves many times when information for one block of the next data is read, and the read processing takes a long time.

[0034] On the other hand, according to the processing of the access control device 10 of the present disclosure, information on multiple blocks included in a certain data item is read out in sequence and continuously. In this case, the number of times the head needs to move from one data item to another and the time required for cueing can be reduced. In other words, when data n includes information on blocks with multiple block numbers, that information is stored in a small area on the magnetic tape 20. Therefore, when information on blocks with multiple block numbers included in data n is read out in sequence, the number of times the head needs to move for the information on the blocks with each block number is reduced, and the read process can be shortened.

[0035] Figure 6 shows two different access control processes in chronological order. In FIG. 6, the left side shows the access control process by the related access control device, and the right side shows the access control process by the access control device 10 of the present disclosure.

[0036] In Figure 6, the access command includes instructions to read data 1, data 2, and data 3, where data 1 includes three blocks, blocks s1-1 to s1-3, data 2 includes two blocks, blocks s2-1 to s2-2, and data 3 includes five blocks, blocks s3-1 to s3-5.

[0037] According to the access control process by the related access control device on the left side of Fig. 6, the process of locating each data is performed eight times from S81 to S88 by the process of Fig. 5. According to the access control process by the related access control device, the process of moving the head 30 to the locating position needs to be performed eight times, and each movement of the head 30 takes time.

[0038] On the other hand, according to the access control by the access control device of the present disclosure shown on the right side of FIG. 6, the process of cueing is performed three times, from S91 to S93, due to the process of FIG.

[0039] If the information of multiple blocks contained in the data is read in the order of block numbers, the search operation becomes unnecessary.On the other hand, in related access control devices, after reading the information of a block with a block number of one piece of data, the information of the block with a block number of the next piece of data is read, and this process is repeated, which makes the search operation time-consuming.

[0040] FIG. 7 is a functional block diagram of an access control device according to another embodiment. FIG. 8 is a diagram showing a processing flow of the access control device according to another embodiment. The access control device 10 includes at least a control means 101 for accessing information on a magnetic tape 20 that stores a group of one or more blocks as one unit of data. Based on an access command including the data numbers of one or more pieces of data, the control means 101 waits for access processing of data having a data number other than the specified one of the data numbers (step S801). The control means 101 starts the access process for the data of the identified one of the data numbers, and sequentially accesses each of one or more blocks corresponding to the data of the data number (step S802). After completing access to all block units corresponding to the data of the identified data number, the control means 101 identifies one of the other waiting data numbers, starts access processing for the data of the identified data number, and repeats the access processing in order for each of one or more block units included in the data of the data number (step S803).

[0041] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure.

[0042] Some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0043] (Appendix 1) a control means for reading information from a magnetic tape that stores one or more blocks of data as a unit of data; the control means waits for a read process of data having a data number other than the specified one of the data numbers based on a read access command including the data numbers of one or more of the data; starting a read process of data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and reading the data in the block units in order; After the reading of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, a read process of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the read process of the block units is repeated in order. Access control device.

[0044] (Appendix 2) a storage means for storing block numbers of the blocks included in the one unit of data; The control means reads from the storage means a block number of a block unit corresponding to the data of the data number included in the access command, and determines whether or not there is a block unit corresponding to the data of the data number included in the access command. 10. The access control device of claim 1.

[0045] (Appendix 3) The control means controls the movement of a header to a read position of the one or more block units included in the data of the identified data number on the magnetic tape in order. 10. The access control device according to claim 1 or 2.

[0046] (Appendix 4) the control means stores a data number other than the specified one of the data numbers based on the access command as a data number of data waiting to be read; After the read process for each of the one or more blocks included in the data of the identified data number is completed, the process of identifying data of the one data number for which the read process has not been performed from the stored data numbers is repeated. 4. An access control device according to any one of claims 1 to 3.

[0047] (Appendix 5) A control means for reading information from a magnetic tape that stores one or more blocks of data as a unit of data, waiting for a read process of data having a data number other than the specified one of the data numbers based on a read access command including the data numbers of one or more of the data; starting a read process of data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and reading the data in the block units in order; After the reading of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, a read process of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the read process of the block units is repeated in order. Access control methods.

[0048] (Appendix 6) storing the block numbers of the blocks included in the one unit of data in a storage means; A block number of a block unit corresponding to the data of the data number included in the access command is read from the storage means, and it is determined whether or not there is a block unit corresponding to the data of the data number included in the access command. 6. The access control method according to claim 5.

[0049] (Appendix 7) Control is performed so that a header is moved to a read position of the one or more block units included in the data of the specified data number in order on the magnetic tape. 10. The access control method according to claim 5 or 6.

[0050] (Appendix 8) storing a data number other than the one identified among the data numbers based on the access command as a data number of data waiting to be read; After the read process for each of the one or more blocks included in the data of the identified data number is completed, the process of identifying data of the one data number for which the read process has not been performed from the stored data numbers is repeated. 8. An access control method according to any one of Supplementary Note 5 to Supplementary Note 7.

[0051] (Appendix 9) A computer having a control means for reading information from a magnetic tape that stores one or more blocks of data as a unit of data, waiting for a read process of data having a data number other than the specified one of the data numbers based on a read access command including the data numbers of one or more of the data; starting a read process of data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and reading the data in the block units in order; After the reading of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, a read process of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the read process of the block units is repeated in order. A program that executes a process.

[0052] (Appendix 10) The computer includes a storage means for storing block numbers of the blocks included in the data unit, A block number of a block unit corresponding to the data of the data number included in the access command is read from the storage means, and a process of determining whether or not there is a block unit corresponding to the data of the data number included in the access command is executed. 10. The program described in Appendix 9.

[0053] (Appendix 11) The control means controls the movement of a header to a read position of the one or more block units included in the data of the identified data number on the magnetic tape in order. 10. A program according to claim 9 or 10.

[0054] (Appendix 12) the control means stores a data number other than the specified one of the data numbers based on the access command as a data number of data waiting to be read; After the read process for each of the one or more blocks included in the data of the identified data number is completed, the process of identifying data of the one data number for which the read process has not been performed from the stored data numbers is repeated. 12. A program according to any one of claims 9 to 11. [Explanation of symbols]

[0055] 10. Access control device 11. Exclusive control unit (control means 101) 20. Magnetic tape 30 heads 100... Magnetic tape drive 200 LTFS

Claims

1. a control means for reading information from a magnetic tape that stores one or more blocks of data as a unit of data; the control means waits for a read process of data having a data number other than the specified one of the data numbers based on a read access command including the data numbers of one or more of the data; starting a read process of data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and reading the data in the block units in order; After the reading of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, a read process of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the read process of the block units is repeated in order. Access control device.

2. a storage means for storing block numbers of the blocks included in the one unit of data; The control means reads from the storage means a block number of a block unit included in data corresponding to the data number included in the access command, and determines whether or not there is a block unit corresponding to the data of the data number included in the access command. The access control device according to claim 1 .

3. The control means controls the movement of a header to a read position of the one or more block units included in the data of the identified data number on the magnetic tape in order. The access control device according to claim 2 .

4. the control means stores a data number other than the specified one of the data numbers based on the access command as a data number of data waiting to be read; After the read process for each of the one or more blocks included in the data of the identified data number is completed, the process of identifying data of the one data number for which the read process has not been performed from the stored data numbers is repeated. The access control device according to claim 3 .

5. a control means for writing information onto a magnetic tape that stores one or more blocks of data as a unit of data; the control means waits for a write process of data having a data number other than the specified one of the data numbers based on a write access command including one or more data numbers of the data; starting a write process of data of a specified one of the data numbers, determining whether it is necessary to write the one or more blocks corresponding to the data of the specified data number, and writing the data in the blocks in order; After writing all block units corresponding to the data of the specified one data number has been completed, one of the other waiting data numbers is specified, a write process of the data of the specified one data number is started, it is determined whether writing of the one or more block units corresponding to the data of the specified data number is necessary, and the process of writing the block units is repeated in order. Access control device.

6. The control means specifies the number of block units corresponding to the data included in the access command, and performs the write process for each block unit of the number corresponding to the data corresponding to the data number included in the access command. The access control device according to claim 5 .

7. The control means controls the movement of a header to a write position of the one or more block units corresponding to the data of the identified one data number on the magnetic tape in order. The access control device according to claim 6 .

8. the control means stores a data number other than the specified one of the data numbers based on the access command as a data number of data waiting to be written; After the write process for each of the one or more blocks corresponding to the data of the identified data number is completed, the process of identifying the data of the one data number for which the write process has not been performed from the stored data numbers is repeated. The access control device according to claim 7 .

9. A control means for accessing information on a magnetic tape that stores one or more blocks of data as a unit of data, waiting for access processing of data having a data number other than the specified one of the data numbers based on an access command including the data numbers of one or more of the data; starting an access process for data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and accessing the data in the block units in order; After the access of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, access processing of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the access processing is repeated in order for the block units. Access control methods.

10. A computer having a control means for accessing information on a magnetic tape that stores one or more blocks of data as a unit of data, waiting for access processing of data having a data number other than the specified one of the data numbers based on an access command including the data numbers of one or more of the data; starting an access process for data of a specified one of the data numbers, determining whether or not there are one or more block units corresponding to the data of the specified data number, and accessing the data in the block units in order; After the access of all block units included in the data of the specified one data number is completed, one of the other waiting data numbers is specified, access processing of the data of the specified one data number is started, it is determined whether or not there are one or more block units corresponding to the data of the specified data number, and the access processing is repeated in order for the block units. A program that executes a process.

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