JPH0432419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a sequential file update method suitable for a system equipped with an auxiliary storage device in which sequential files are stored.

[Technical background of the invention]

In conventional sequential files, when dynamically adding, inserting, or deleting data or text, a separate file is generally prepared for updating, and portions that have not changed are copied to the update file, and changed or added portions are An update method was applied in which changes and additional data were added.

[Problems with background technology]

This method requires input/output processing to copy unchanged parts to the updated file, securing a separate file for updating, a so-called work file, and processing to return the updated file to the original file after updating. There was an inconvenience. Therefore, in conventional methods, dynamic changes to sequential files should generally be avoided, since the overhead is large and the processing speed is reduced, especially in an online, real-time processing environment.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a sequential file update method that allows updating operations such as additions and deletions to sequential files to be performed efficiently and easily even in an online, real-time processing environment. It is about providing.

[Summary of the invention]

In order to achieve the above object, the present invention proposes a new sequential file structure. The sequential file proposed by the present invention consists of a series of pages of a fixed size, which are numbered.
Each page number is appended with page information indicating its own page number C, the page number P of the previous page, the page number N of the next page, and the number n of records stored in the page. That is, while the conventional sequential file is a so-called scroll file, the sequential file according to the present invention is a so-called loose-leaf file having a page link mechanism. As described above, by adding the page numbers of the pages before and after each page to each page, the logical order relationship is maintained.

Furthermore, in order to access files, the present invention uses a file control block (hereinafter referred to as FCB), which is an information list for managing extents (storage address areas in auxiliary storage devices) occupied by various sequential files on a file-by-file basis. )
For files written in FCB, a file access control block (hereinafter referred to as FAB) is used to manage the current location of files being accessed by each program (task). . This FAB is initialized in the main memory by the arithmetic and control unit when an open command to open the first page (which may be a designated page) of a file is issued for each task by the program. Furthermore, when the arithmetic and control unit outputs an open command, the FCB corresponding to the file specified by the command is loaded into the main memory. Then, the file access position (page position to be accessed) is determined by a positioning command from the arithmetic and control unit, and the contents of FAB on the main memory are also made to match the determined position.

If a record addition (including insertion) command is issued from the arithmetic control unit in this state, a new record will be added to the corresponding page based on the number of stored records n in the page information of the page at the determined file access position. It is checked whether there is space to add a record, and if there is space, a new record is added to the page and the number n of stored records in the page information is updated. On the other hand, if there is no space, based on the number of stored records n in the page information of the previous page indicating the previous page number P or the next page indicating the next page number N in the page information, the adjacent page is It is checked whether there is space or not, and if there is space on the adjacent page, the necessary records are moved from the page to the adjacent page, a free area is created on the page, and a new record is stored in that free space. At the same time, the number n of stored records in each page information of the relevant page and the adjacent page to which the above-mentioned necessary record has been transferred is updated.

Additionally, when a record deletion command is issued from the arithmetic control unit, the specified record is deleted from the page at the file access position determined above.
The number n of stored records in the page information of the same page is updated.

In other words, the present invention has a configuration in which sequential files are managed on a page-by-page basis, and managed in such a way that the logical order relationship of each page is maintained. This allows file updates to be performed in units of units, making it possible to update files by partially modifying pages.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an information processing system to which the present invention is applied, where 11 is an arithmetic and control unit that controls the entire system, and 12 is a main memory (hereinafter referred to as
MM), 13 is an auxiliary storage device such as a magnetic disk storage device. The auxiliary storage device 13 stores various sequential files. This file is not necessarily stored in a physically continuous area in the auxiliary storage device 13,
For example, several physically discontinuous extents (one extent is a physically contiguous area)
It is divided and stored in . The sequential file is made up of a series of pages of a fixed size and numbered. Each page has its own page number (own page number) C, as shown in Figure 2.
Page information consisting of the page number of the previous page (previous page number) P, the page number of the next page (next page number) N, and the number of records stored on that page (number of stored records) n is added. There is. For example, the pages are assigned natural numbers 1, 2, 3, etc. in order from the beginning of the file, and are managed independently of physical address information (extents). By having the page information shown in FIG. 2 described above, each of these pages maintains a logical order relationship (page link) as shown in FIG. 3. Further, the auxiliary storage device 13 stores an FCB (file control block), which is an information list indicating the auxiliary storage areas occupied by the various sequential files described above, for each file. This FCB can also be said to be an information list for managing several extents occupied by the file in accordance with the growth and development of the file. The contents of the FCB include information indicating the logical order of each extent, the start address and size of each extent, the page size, the number of pages that can be stored in the extent, the record length, the number of records that can be stored in the page, and page links. This may be the start address of a vacant page.

14 is an auxiliary storage control device. The auxiliary storage controller 14 is connected to the input/output bus 15 from the arithmetic controller 11.
Auxiliary storage device 1
It has a function as a so-called file server that controls 3 and performs file updates and the like. In response to an open command from the arithmetic and control unit 11, the auxiliary storage device 14 stores the FCB corresponding to the specified file.
is now loaded into MM12. M.M.
FAB (File Access Control Block), which is an information list for managing the current location of files accessed by each program (task), is also placed in 12. The contents of the FAB are a page number and a record number (information indicating what page and what record). This FAB is initially set on the MM 12 by the arithmetic and control unit 11 when the program issues an open command for each task, and a plurality of FABs may exist for the same file.
This is because, in this embodiment, concurrent access (simultaneous access) under multiprogramming is permitted in units of records or blocks. Further, as shown in FIG. 4, the auxiliary storage control device 14 stores the file name, page number, file reference/update flag F ₁ , page information change flag F ₂ ,
and a concurrent access management list consisting of the number of tasks T. This list shows which page of which file is currently being viewed or updated, and whether the page information has been changed.
It also shows the number of tasks accessing that page, and is placed on the MM 12, for example.

Referring to Figure 1 again, 16 is a DMA (Direct
Memory Access) bus 17 is an input/output channel that controls data transfer between MM 12 and auxiliary storage device 13.

Next, one embodiment of the present invention will be described. In this embodiment, file updates such as addition (insertion) and deletion of (data) records are performed in the following steps.

Opening the target file Positioning the target file (determining the current status) Adding (inserting)/deleting target (data) records Closing the target file First, opening the target file will be explained. If the command read from the MM12 is an open command, the arithmetic control unit 12 sets the FAB indicating the first record of the first page (page 1) of the file specified by the command to the MM12. , gives an open command to the auxiliary storage control device 14 via the input/output bus 15. The auxiliary storage control device 14 reads the FCB corresponding to the file specified by this open command from the auxiliary storage device 13, loads it into the MM 12, and then issues a termination interrupt to the arithmetic control device 11. This is the opening of the target file.

Next, the positioning of the target file (determining the current) will be explained. When the open instruction is executed, the get instruction or position instruction is set to MM1.
2 (may be read ahead),
A corresponding command is given from the arithmetic control device 11 to the auxiliary storage control device 14. The get command is a command for reading the target record (record indicated by FAB) at the addition (insertion)/deletion position, and the position command is a command for positioning. The position command allows positioning by specifying a page number or relative specification such as the number of pages after the page indicated by FAB. When the auxiliary storage control device 14 receives a get command, it determines the physical address position in the auxiliary storage device 13 of the corresponding record in the corresponding page based on the FAB and FCB on the MM 12. The auxiliary storage controller 14 reads the corresponding record from the address position and loads it into the MM 12, and
Update FAB on MM12. This allows FAB
will now point to the next record. The arithmetic control unit 11 refers to the record loaded into the MM 12, and if it is not the desired record as the target of the addition (insertion)/deletion position, it issues a get command to the auxiliary storage control unit 14 again. and the desired record is
By loading the data into the MM 12, the arithmetic and control unit 11 determines whether the target addition (insertion)/deletion position has been determined.

Further, when the auxiliary storage control device 14 receives a position command (instead of the above-mentioned get command), it updates the contents of FAB on M12 in accordance with this command. This determines the file access position. The above is the positioning of the target file.

Next, addition (insertion)/deletion of target (data) records will be explained, first taking the case of record addition (insertion) as an example. Assume that after a get command or a position command is issued as described above and, for example, an addition position is determined, a put command is issued to instruct the addition (insertion) of a new record. The arithmetic control unit 11 sends a command corresponding to the relevant command to the auxiliary storage control unit 1 via the input/output bus 15.
Give to 4. The auxiliary storage control device 14 determines the physical address position of a page to be accessed, for example, page C, in the auxiliary storage device 13 based on FAB and FCB on the MM 12, and refers to the page information added to the page C. . The auxiliary storage control device 14 then performs the following processing based on this page information.

The auxiliary storage control device 14 determines whether there is space for adding (inserting) a new record to the corresponding page C based on the number n of stored records in the page information. If there is space in the corresponding page C, as shown in FIG. 5A, the auxiliary storage control device 14 adds (inserts) a new record into the page C, as shown in FIG. 5B.

On the other hand, if there is no space on the corresponding page C (Current) as shown in Figure 6 A and Figure 7 B,
The auxiliary storage control device 14 knows the previous page P (Prior) or the next page (Next) based on the previous page number P or next page number N in the page information of the page C, and refers to the page information. Then, based on the number of stored records in this page information, it is determined whether there is space in the adjacent page (previous or subsequent page). As shown in FIG. 6A, for example, if there is space on the previous page P, the auxiliary storage control device 14 transfers the necessary records from the corresponding page C to the previous page P, as shown in FIG. 6B. (overflow processing) to create an empty space on the corresponding page C, and store the new record in this empty area. At this time, the number of stored records in the page information of pages P and C is updated as shown.

On the other hand, if there is no free space in the adjacent page as shown in FIG. (not available). And auxiliary storage control device 14
As shown in FIG. 7B, the necessary record is moved from the corresponding page C to page N', and the new record is stored in page C (whichever of pages C and N' has a larger free space). In addition, the auxiliary storage control device 1
Step 4 updates the adjacent page information (ie, previous page number, next page number) in the page information of pages C, N', and N as shown in the figure in order to maintain the logical order relationship of each page. At this time, the number of stored records in the page information of pages C and N' is also updated. Additionally, the start address of the page-linked free page in the FCB is also updated.

Next, record deletion will be explained. In this case, when the get command or position command is executed and the deletion position is determined as described above, a DELETE command is issued to instruct deletion of the record. The auxiliary storage control device 14 refers to the page information added to the page to be deleted, as in the case of addition (insertion) described above. Then, the auxiliary storage control device 14 performs the following processing based on this page information.

That is, the auxiliary storage control device 14 pads the deleted records within the corresponding page. At this time, if an instruction to effectively utilize the area has been issued, the auxiliary storage control device 14 determines whether or not the only records stored in the page are records to be deleted, based on the number of stored records. If there is only the target record in the relevant page, the auxiliary storage control device 14 removes the relevant page from the valid page list and places it in the free page list (page deletion), and also deletes the next page number and subsequent page number in the page information of the previous page. Update the previous page number in the page information of the page. Furthermore, if there are records other than the target record in the corresponding page, the auxiliary storage control device 14 determines whether the number of stored records is less than or equal to a predetermined number. If the number is less than a predetermined number, the auxiliary storage control device 14 performs a merge check to see if it is possible to merge the pages with adjacent pages, and determines whether the records stored in the relevant page and the adjacent pages can be stored in one page. If so, merge them into one page (merging process). Pages that are no longer needed due to this merging are placed on a free page list and prepared for future page reuse.

Next, concurrent access under multiprogramming will be explained. In the present invention, files can be updated page by page instead of file by file as in the past, so even if one task is updating a file, it is possible for the other task to refer to the file (as long as the page is different). Special concurrent access is possible. In this embodiment, a simultaneous access management list (see FIG. 4) is prepared as described above so that such concurrent access can be performed correctly under any conditions. This list is created on the MM by the auxiliary storage control device 14. Now, add A as the file name in the above list.
Assume that C is written as the page number. In this state, another task uses the same file A.
When attempting to refer to or update page C at the same time, the auxiliary storage control device 14 determines whether the corresponding file name and page number exist in the list. If the file exists as described above, the auxiliary storage control device 14 checks whether the corresponding file reference/update flag _F1 is "1" or "0". If F ₁ = “1”, the corresponding page C is in an updated state, so the auxiliary storage control device 14 updates the page C.
It is assumed that simultaneous access to is prohibited. On the other hand, if F ₁ = "0", the auxiliary storage control device 14 checks whether the number of tasks T is "0" and determines whether simultaneous access to the corresponding page C is possible. . (When F ₁ = “0”) T is “0”
If not, this indicates that the corresponding page C is being referred to. In this case, if the other task is requesting to refer to page C, simultaneous access is permitted, and if the other task is requesting updating of page C, simultaneous access is prohibited. On the other hand, (F ₁ = “0”
) If T is "0", this indicates that the corresponding page C has not been referenced, and simultaneous access is permitted for both reference and update requests. If the auxiliary storage control device 14 determines that simultaneous access is possible, it sets T to +1, and if it is a file update, sets _F1 , and refers to or updates the corresponding page C.

On the other hand, if the corresponding file name and page number do not exist in the above list, the auxiliary storage control device 14 writes the file name and page number into the free area of the list (including the area where T = "0"). At the same time, T=``1'' is written, and _F1 is set if the file is updated. Thus, the relevant page is referenced or updated.

The task that is updating the file (auxiliary storage control device 14) will update the file if there is a task that is accessing the adjacent page (this can be determined from the list above), and if updating within the same page is not possible. , the division process (see FIG. 7, a, b) is performed without performing the overflow process (see, FIG. 6, a, b). This is to prevent the stored records of adjacent pages from being changed. In this case, since the page link changes, the task updating the above file will use the corresponding page information change flag in the above list.
Set F ₂ . In contrast, the task (auxiliary storage control device 14) that refers to the above-mentioned adjacent page
If the page information has been taken in at the time when the page information change flag _F2 is set, the page information is read out again. This makes it possible to refer to the correct record after updating the file. Note that when the auxiliary storage control device 14 finishes executing a file reference or update request from a certain task,
The corresponding T in the above list is decremented by 1, and if the file update is completed, F ₁ and F ₂ are reset.

By the way, in the present invention, by creating a type of index page that holds the number of stored records for each page, it is possible to directly access a dynamic sequential file using a record number or the like. The present invention can also be applied to the data record portion of an indexed sequential file.

〔Effect of the invention〕

As detailed above, according to the sequential file update method of the present invention, various effects listed below can be achieved.

Data records can be added (inserted) and deleted in sequential files.

When adding (inserting) or deleting, there is no need for a work file as in the past, and only partial page modification is required. Concurrent access is possible.

File area can be used effectively.

The program for modifying sequential files can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is a diagram showing the format of page information applied in the above embodiment, Figure 3 is a diagram to explain a page sequence that maintains a logical order relationship, and Figure 4 is an example of a simultaneous access management list. The figures shown in Fig. 5 A and B, Fig. 6 A and B, and Fig. 7 A and B are for explaining the state of the page before and after record addition (insertion), respectively. B is a state diagram after addition (insertion). 11... Arithmetic control unit, 12... Main memory (MM),
13... Auxiliary storage device, 14... Auxiliary storage control device.

Claims (1)

[Scope of Claims] 1. A sequential file consisting of a row of pages of a constant size with page numbers, each page having its own page number C, previous page number P, page number N of the next page, and An auxiliary storage device that stores various sequential files to which page information indicating the number of stored records n is added, as well as a file control block that is an information list for managing extents occupied by these files on a file-by-file basis. and an arithmetic control unit that initializes a file access control block in main memory that indicates the current location of the file specified by the command when the program issues an open command for each task; In accordance with the directive,
means for reading a file control block corresponding to a designated file from the auxiliary storage device and loading it into the main memory; means for updating a corresponding file access control block in memory, and referring to the page information of the page of the determined file access position in response to the record addition command from the arithmetic and control unit; additional means for adding records on a page-by-page basis and updating page information on the update page; and deleting a designated record from the page at the determined file access position in response to a record deletion command from the arithmetic and control unit. and a deletion means for updating the number n of stored records in the page information of the same page, and the adding means updates a new record on the corresponding page based on the number n of stored records in the page information referred to above. Check whether there is space to add a new record, and if there is space, add a new record in the page and increase the number of stored records n in the page information.
is updated, and if there is no space, the next page is updated based on the number of stored records n in the page information of the previous page indicated by the previous page number P or the next page indicated by the next page number N in the page information. Check whether there is space, and if there is space on the adjacent page, move the necessary records from the page to the adjacent page to create a free space on the page, store the new record in the free space, and move the necessary records from the page to the neighboring page. and updating the number n of stored records in each page information of the adjacent page to which the necessary record has been transferred.