Access control device, access control method, program

Abstract

This invention provides an access control device that enables more efficient access to information on a magnetic tape that stores one or more block-based units as a single data unit. [Solution] The system includes a control means for reading information from a magnetic tape that stores one or more block units as a single data unit. Based on a read access command that includes the data numbers of one or more data, the control means waits for the data reading process of data numbers other than the one specified among the data numbers. The system starts the data reading process for the one specified data number, determines whether there are one or more block units corresponding to the data of that data number, and reads them sequentially in block units. After the reading of all block units contained in the data of the specified data number is completed, the system identifies one of the other waiting data numbers and repeats the reading process 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 Art

[0002] In the technology of reading information from a magnetic tape and writing information to a magnetic tape, there is LTFS (Linear Tape File System). In reading and writing information using LTFS, a user can intuitively write and read information in file units in the same way as performing operations of writing information to and reading information from a storage device such as a hard disk while visually recognizing a terminal in a PC or the like.

[0003] For example, Patent Document 1 discloses a technique aimed at reducing the access waiting time for a magnetic tape in a system for managing data stored on a magnetic tape using the file system of LTFS.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technique described in Patent Document 1 is a technique aimed at reducing the access waiting time for a magnetic tape in a library device that includes a plurality of drives and performs data synchronization processing between at least two magnetic tapes among a plurality of recording media using the plurality of drives.

[0006] Here, there is a need for a technique to more efficiently access information to one magnetic tape that stores a collection of one or more block units as one unit of data.

[0007] The purpose of this 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 one or more block units as a single unit of data, wherein the control means waits for the data reading process of a data number other than one of the data numbers that has been identified, based on a read access command that includes one or more data numbers of the data, starts the data reading process of the one data number that has been identified, determines whether or not there is one or more block units corresponding to the data of that data number, reads the block units in order, and after the reading of all block units contained in the data of the one data number that has been identified has been completed, identifies one of the other data numbers that has been waiting, starts the data reading process of the one data number that has been identified, determines whether or not there is one or more block units corresponding to the data of that data number, and repeats the process of reading the block units in order.

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

[0010] A program according to one aspect of the present disclosure causes a computer equipped with control means for accessing information on a magnetic tape that stores a collection of one or more block units as a single unit of data, to perform the following process based on an access command including one or more data numbers of the data: wait for access processing of data for data numbers other than one specified among the data numbers; start access processing of data for one specified data number among the data numbers; determine whether there is one or more block units corresponding to the data for that data number; access the block units sequentially; after access to all block units contained in the data of the specified data number is completed, identify one of the other waiting data numbers; start access processing of data for that specified data number; determine whether there is one or more block units corresponding to the data for that data number; and repeat the access processing for the block units sequentially. [Effects of the Invention]

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

[0012] [Figure 1] This is a schematic diagram of a magnetic tape system according to one embodiment of the present disclosure. [Figure 2] This is a hardware configuration diagram of an access control device according to one embodiment of the present disclosure. [Figure 3] This figure shows the structure of data stored in a magnetic tape according to one embodiment of the present disclosure. [Figure 4] This is the first figure showing the processing flow of an access control device according to one embodiment of the present disclosure. [Figure 5] This diagram shows the processing flow for the related access control device. [Figure 6] This diagram shows two different access control processes arranged chronologically. [Figure 7] This is a functional block diagram of an access control device according to another embodiment. [Figure 8] This figure shows the processing flow of an access control device according to another embodiment. [Modes for carrying out the invention]

[0013] Each embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram of a magnetic tape system according to one embodiment of the present disclosure. The magnetic tape system 1 of this disclosure comprises a magnetic tape drive 100 and an LTFS200 (Linear Tape File System). The magnetic tape drive 100 and the LTFS200 are connected by a communication link.

[0014] The magnetic tape drive 100 includes 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 for reading and writing the magnetic tape 20 based on the control of the access control device 10. The access control device 10 exhibits the function of the exclusive control unit 11 by executing an exclusive control program.

[0015] Here, when handling the magnetic tape 20 in the magnetic tape drive 100, a highly convenient LTFS is used. LTFS is a file system that enables handling data on the magnetic tape 20 in file units. Dedicated software was required for the operation of the magnetic tape 20, but LTFS enables utilization with simple operations like data in an HDD.

[0016] When LTFS reads data, it gives the magnetic tape drive 100 the target data number, data location (recording position on the magnetic tape 20), and data capacity (number of data blocks) as parameters of the access command, reads the data in block units, and sends the data that becomes one file to a higher-level device or the like.

[0017] Figure 2 is a hardware configuration diagram of an access control device according to an embodiment of the present disclosure. As shown in Figure 2, the access control device 10 may be a computer including 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] Figure 3 is a diagram showing the structure of data stored in a magnetic tape according to an embodiment of the present disclosure. As shown in FIG. 3, the magnetic tape 20 stores a collection of one or more block units as one unit of data. Specifically, FIG. 3 shows a state in which n pieces of data, namely data 1, data 2, data 3, …, data n-1, and data n, are recorded on the magnetic tape 20. Data 1 shows a state in which information of three block units, namely block 1-1, block 1-2, and block 1-3, is recorded. Data 2 shows a state in which information of two block units, namely block 2-1 and block 2-2, is recorded. Data 3 shows a state in which information of five block units from block 3-1 to block 3-5 is recorded. Data n-1 shows a state in which information is recorded in five block units from block (n-1)-1 to block (n-1)-5. Data n-1 shows a state in which information is recorded in five block units from 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] Based on a read access command including the data numbers of one or more pieces of data, the exclusive control unit 11 of the access control device 10 specifies one data number and waits for the read processing of the data with data numbers other than the specified data number by exclusive control. The exclusive control unit 11 starts the read processing of the data with the specified one data number, determines whether there are one or more block units corresponding to the data with the data number, and reads them in order by block unit. After the reading of all block units included in the data with the specified one data number is completed, the exclusive control unit 11 specifies one of the other waiting data numbers, starts the read processing of the data with the specified one data number, determines whether there are one or more block units corresponding to the data with the data number, and repeats the process of reading in the order of the block units.

[0021] Here, the magnetic tape 20 consists of multiple tracks, and the 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 unwinding the magnetic tape 20 to move the head 30 to align with the start position of data block reading or writing is called cueing.

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

[0023] First, the LTFS200 receives an access command from the higher-level device. The access command may include a data number. For example, suppose the access command includes data n (n: number). Let's say n = 1, 2, 3. In other words, the access command commands access to data 1, data 2, and data 3. Let's also assume that this access command includes read commands for each data. The LTFS200 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. This causes the exclusive control unit 11 to start data read processing (step S101). The exclusive control unit 11 identifies data 1, which has the smallest value of n among the data n numbers included in the access command, and decides to apply exclusive control to the other data 2 and data 3. The exclusive control unit 11 records the information of data 2 and data 3, which it has decided to apply exclusive control to, in the storage unit (step S102).

[0025] When access control (data read) is performed, the exclusive control unit 11 controls the movement of the head 30 on the magnetic tape 20 (head positioning) based on the recording position of the identified data n (n=1) (step S103). The recording position of data n may be stored in the storage device 104 in advance for each piece of data n. When access control (data read) is performed, the exclusive control unit 11 identifies the block ns included in the identified data n (n=1) (step S104). For example, the block with block number s included in data n will be called block ns. Information about block ns may be included in the access instruction, or the access control device 10 may store the information about the block included in data n in the storage device 104 in advance. Assume that the 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 the data ns, which is block number 1 included in data 1. In other words, the exclusive control unit 11 identifies the block ns with the smallest block number s among the blocks included in the identified data n for access control.

[0026] The exclusive control unit 11 controls the head 30 to move to the reading position of block 1-1 on the magnetic tape 20 so that it can read the information of the identified block 1-1. The reading position of each block number may be stored in the storage device 104 in advance, or the access command may include information about the reading position. As a result, the head 30 moves to the reading 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 reads the information of block 1-1 from the head 30 (step S105). The exclusive control unit 11 outputs the information of block 1-1 to the LTFS 200.

[0027] The mutual exclusion 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). In other words, the mutual exclusion control unit 11 determines whether block numbers 1-2 are included in data 1 based on the new block number s = 1 + 1 = 2. Since block numbers 1-2 are included in data 1, the mutual exclusion control unit 11 controls the head 30 to move to the reading 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 reading position of block 1-2 on the magnetic tape 20. The mutual exclusion control unit 11 instructs the head 30 to read block 1-2 and reads the information of block 1-2 from the head 30. The mutual exclusion control unit 11 outputs the information of block 1-2 to the LTFS 200. The mutual exclusion control unit 11 similarly determines whether the new block number s is included in data n, obtains the information of block 1-3, and outputs the information of block 1-3 to the LTFS 200.

[0028] In step S106, if there is no next new block number included in data n, the exclusive control unit 11 sets s=1 and identifies the next largest new data number n from the storage unit recorded in the exclusive control in step S102 (step S107). In other words, 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 recorded by the exclusive control. The exclusive control unit 11 determines whether the new data number n is greater than the largest number D among the data numbers identified in the access instruction (step S108). If the new data number n is greater than the largest number D among the data numbers identified in the access instruction, the exclusive control unit 11 terminates the data read. If the new data number n is less than the largest number D among the data numbers identified in the access instruction, the exclusive control unit 11 identifies the data and starts processing in step S103. In other words, the exclusive control unit 11 similarly reads the blocks of block 2-s included in data 2, starting from block 2-1.

[0029] Figure 5 shows the processing flow for the related access control device. Next, we will explain the processing flow of the related access control device. When the associated access control device starts reading the first data n with the smallest n among the data n included in the access command (step S61), it controls the position of the head relative to the magnetic tape 20 to move (head position) so that the information of data n can be read (step S62). Once the associated access control device controls the position of the head, it performs a block read, that is, reading the information of a block (step S63).

[0030] In this block read, the associated access control device sets block number s=1 and determines whether or not block ns is included in the data n (step S631). If block ns is included, the head 30 is moved to the position of block ns (step S632), the information of block ns is read (step S633), and the block read process is terminated. In other words, even if the data n contains multiple blocks of block ns, the associated access control device stops reading information from other blocks included in the data n once it has finished reading the information of one block ns.

[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 greater than the largest data number D identified in the access instruction (n>D) (step S64). If the new data number n is less than the largest data number D identified in the access instruction, the access control device reads the information of one block number in that data number n and terminates the process, similar to the process in step S63 (steps S631 to S633). In other words, the associated access control device reads the block information of one block number in the data of one data number and stops the read process. The associated access control device then performs the read process similarly for the data of the other data numbers included in the access instruction.

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

[0033] According to the processing of such related access control devices, when reading from multiple data contained in an access command, the process of reading one block at a time is performed sequentially for each data, and when the information of one block has been read from all the data, the process of reading the information of the next block sequentially from all the data is repeated. Therefore, in the processing of the related access control device, when the information of one block of one data is read, the number of head movements when reading the information of one block of the next data is large, and the reading process takes a long time.

[0034] On the other hand, according to the processing of the access control device 10 of this disclosure, information from multiple blocks contained in a given data is read sequentially. In this case, the number of head movements from one data to another and the time required for cueing can be reduced. That is, when data n contains information from blocks with multiple block numbers, that information is stored in a narrow area of ​​the magnetic tape 20. Therefore, when sequentially reading information from blocks with multiple block numbers contained in data n, the number of head movements for the information of each block number is reduced, and the reading process can be shortened.

[0035] Figure 6 is a diagram showing two different access control processes arranged in chronological order. In Figure 6, the left side shows the access control processing by the related access control device, and the right side shows the access control processing by the access control device 10 of this disclosure.

[0036] Figure 6 shows an example where the access instruction includes read instructions for data 1, data 2, and data 3. Data 1 contains three blocks s1-1 to s1-3, data 2 contains two blocks s2-1 to s2-2, and data 3 contains five blocks s3-1 to s3-5.

[0037] According to the access control processing by the related access control device on the left side of Figure 6, the process of finding the beginning of each data is performed eight times from S81 to S88 as shown in Figure 5. According to the access control processing by the related access control device, it is necessary to move the head 30 to the found position eight times, and each movement of the head 30 takes time.

[0038] On the other hand, according to the access control device of the present disclosure shown on the right side of Figure 6, the process in Figure 4 results in three cueing processes from S91 to S93.

[0039] If the information from multiple blocks contained in the data is read in the order of block numbers, the need for cueing is eliminated. On the other hand, the related access control device reads the information from one block number in one data set, then reads the information from one block number in the next data set, and repeats this process, which takes time for cueing.

[0040] Figure 7 is a functional block diagram of an access control device according to another embodiment. Figure 8 shows the processing flow of an access control device according to another embodiment. The access control device 10 includes a control means 101 for accessing information on a magnetic tape 20 that stores at least one block-based grouping as a single data unit. The control means 101 waits for access processing of data with data numbers other than the one specified among the data numbers, based on an access command that includes the data numbers of one or more data (step S801). The control means 101 initiates the data access process for one of the identified data numbers and sequentially accesses one or more block units corresponding to the data for that data number (step S802). After completing access to all block units corresponding to the data of a single identified data number, the control means 101 identifies one of the other pending data numbers, starts accessing the data of that identified data number, and repeats the access process sequentially for one or more block units contained in the data of that data number (step S803).

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

[0042] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0043] (Note 1) It includes a control means for reading information from a magnetic tape that stores one or more block units as a single data unit, The control means waits for the data read process of a data number other than the one specified among the data numbers, based on a read access command that includes one or more data numbers of the data. The process of reading the data for one of the identified data numbers is started, and it is determined whether there is one or more block units corresponding to the data for that data number, and the block units are read out in order. After reading all block units contained in the data of the identified data number, one of the other pending data numbers is identified, and the data reading process for that identified data number is started. It is then determined whether there are one or more block units corresponding to the data of that data number, and the process of reading the block units in order is repeated. Access control device.

[0044] (Note 2) The system includes a storage means for storing block numbers for block units included in the aforementioned unit of data, The control means reads the block number of a block unit corresponding to the data of the data number included in the access instruction from the storage means and determines whether or not there is a block unit corresponding to the data of the data number included in the access instruction. The access control device described in Appendix 1.

[0045] (Note 3) The control means controls the header to move sequentially to the reading position of the block unit on the magnetic tape for each of the one or more block units contained in the data of the identified data number. The access control device described in Appendix 1 or Appendix 2.

[0046] (Note 4) The control means stores, based on the access command, a data number other than the one specified among the data numbers as the data number of the data awaiting read processing. After the read process for one or more block units contained in the data of one identified data number is completed, the process of identifying the data of one data number that has not been read from the stored data numbers is repeated. An access control device as described in any one of the appendices 1 through 3.

[0047] (Note 5) A control means for reading information from a magnetic tape that stores one or more block units as a single data unit, Based on a read access command that includes one or more data numbers of the aforementioned data, the system waits for the read process of the data number other than the one identified among the aforementioned data numbers. The process of reading the data for one of the identified data numbers is started, and it is determined whether there is one or more block units corresponding to the data for that data number, and the block units are read out in order. After reading all block units contained in the data of the identified data number, one of the other pending data numbers is identified, and the data reading process for that identified data number is started. It is then determined whether there are one or more block units corresponding to the data of that data number, and the process of reading the block units in order is repeated. Access control methods.

[0048] (Note 6) The block number of the block unit included in the aforementioned unit of data is stored in the storage means. The storage means reads the block number of a block unit corresponding to the data of the data number included in the access instruction, and determines whether or not there is a block unit corresponding to the data of the data number included in the access instruction. The access control method described in Appendix 5.

[0049] (Note 7) The system controls the header to move sequentially to the read position of each block unit on the magnetic tape for each of the one or more block units contained in the data of the identified data number. The access control method described in Appendix 5 or Appendix 6.

[0050] (Note 8) Based on the access command, the data numbers other than the one identified from the data numbers are stored as the data numbers of the data awaiting read processing. After the read process for one or more block units contained in the data of one identified data number is completed, the process of identifying the data of one data number that has not been read from the stored data numbers is repeated. The access control method described in any one of the appendices 5 through 7.

[0051] (Note 9) A computer equipped with control means for reading information from a magnetic tape that stores one or more block units as a single data unit, Based on a read access command that includes one or more data numbers of the aforementioned data, the system waits for the read process of the data number other than the one identified among the aforementioned data numbers. The process of reading the data for one of the identified data numbers is started, and it is determined whether there is one or more block units corresponding to the data for that data number, and the block units are read out in order. After reading all block units contained in the data of the identified data number, one of the other pending data numbers is identified, and the data reading process for that identified data number is started. It is then determined whether there are one or more block units corresponding to the data of that data number, and the process of reading the block units in order is repeated. A program that executes a process.

[0052] (Note 10) The computer is equipped with a storage means for storing block numbers for block units included in the aforementioned unit of data, The storage means reads the block number corresponding to the data of the data number included in the access instruction, and executes a process to determine whether or not there is a block unit corresponding to the data of the data number included in the access instruction. The program described in Appendix 9.

[0053] (Note 11) The control means controls the header to move sequentially to the reading position of the block unit on the magnetic tape for each of the one or more block units contained in the data of the identified data number. The program described in Appendix 9 or Appendix 10.

[0054] (Note 12) The control means stores, based on the access command, a data number other than the one specified among the data numbers as the data number of the data awaiting read processing. After the read process for one or more block units contained in the data of one identified data number is completed, the process of identifying the data of one data number that has not been read from the stored data numbers is repeated. The program described in any one of the appendices 9 through 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. It includes a control means for reading information from a magnetic tape that stores one or more block units as a single data unit, The control means waits for the data read process of a data number other than the one specified among the data numbers, based on a read access command that includes one or more data numbers of the data. The process of reading the data for one of the identified data numbers is started, and it is determined whether there is one or more block units corresponding to the data for that data number, and the block units are read out in order. After reading all block units contained in the data of the identified data number, one of the other pending data numbers is identified, and the data reading process for that identified data number is started. It is then determined whether there are one or more block units corresponding to the data of that data number, and the process of reading the block units in order is repeated. Access control device.

2. The system includes a storage means for storing block numbers for block units included in the aforementioned unit of data, The control means reads the block number of a block unit contained in the data corresponding to the data number included in the access instruction from the storage means, and determines whether or not there is a block unit corresponding to the data of the data number included in the access instruction. The access control device according to claim 1.

3. The control means controls the header to move sequentially to the reading position of the block unit on the magnetic tape for each of the one or more block units contained in the data of the identified data number. The access control device according to claim 2.

4. The control means stores, based on the access command, a data number other than the one specified among the data numbers as the data number of the data awaiting read processing. After the read process for one or more block units contained in the data of one identified data number is completed, the process of identifying the data of one data number that has not been read from the stored data numbers is repeated. The access control device according to claim 3.

5. It includes a control means for writing information to a magnetic tape that stores one or more block units as a single data unit, The control means waits for the write process of data with a data number other than the one specified among the data numbers, based on a write access command that includes one or more data numbers of the data. The process of writing data for one of the identified data numbers is initiated, and it is determined whether one or more block units corresponding to the data for that data number need to be written. The data is then written in order, block by block. After all block-level writing corresponding to the data of the identified data number is completed, one of the other pending data numbers is identified, the writing process for the data of that identified data number is started, it is determined whether one or more block-level writings corresponding to the data of that data number are necessary, and the process of writing the blocks in order is repeated. Access control device.

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

7. The control means controls the header to move sequentially to the writing position of the block unit on the magnetic tape for each of the one or more block units corresponding to the data of a single identified data number. The access control device according to claim 6.

8. The control means stores, based on the access command, a data number other than the one specified among the data numbers as the data number of the data awaiting write processing. After the writing process for one or more block units corresponding to the data of a single identified data number is completed, the process of identifying the data of a single data number that has not yet been written 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 block units as a single data unit, Based on an access command that includes one or more data numbers of the aforementioned data, the system waits for access processing of data with data numbers other than the one identified among the aforementioned data numbers. The process of accessing the data of one of the identified data numbers is initiated, and it is determined whether there is one or more block units corresponding to the data of that data number, and the block units are accessed sequentially. After access to all block units contained in the data of the identified data number is completed, one of the other pending data numbers is identified, access processing for the data of that identified data number is started, and it is determined whether there are one or more block units corresponding to the data of that data number, and the access processing is repeated for each block unit in turn. Access control methods.

10. A computer equipped with control means for accessing information on magnetic tape that stores one or more block units as a single data unit, Based on an access command that includes one or more data numbers of the aforementioned data, the system waits for access processing of data with data numbers other than the one identified among the aforementioned data numbers. The process of accessing the data of one of the identified data numbers is initiated, and it is determined whether there is one or more block units corresponding to the data of that data number, and the block units are accessed sequentially. After access to all block units contained in the data of the identified data number is completed, one of the other pending data numbers is identified, access processing for the data of that identified data number is started, and it is determined whether there are one or more block units corresponding to the data of that data number, and the access processing is repeated for each block unit in turn. A program that executes a process.

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