JPS62239248A - Physical clustering system - Google Patents

Abstract

PURPOSE:To reduce the time when an external storage device is occupied and I/O loads by storing an updated page close to a frame storing a page before update. CONSTITUTION:When data base information is stored in the external storage device in terms of a data base system employing a shadow paging system, pages are previously stored for the unit of 1-m control areas by securing idle frames. At the time of update, having been updated pages are stored in the idle frames in the control area 1-m where pages to be updated exist. Thus scattering is suppressed, and the number of times seeking and searching the external storage device can be reduced at the time of continuous input of pages.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention uses a physical clustering method, that is, a database system that supports shadow paging. This is related to the method of storing data in .

[Conventional technology]

Regarding the shadow paging method, for example, J in
Gray et al, “The Recovery
Manager of the System RDa
tabase Manager” acm comp-
uting 5urveys, vol. 13. &2(1
981).

To summarize, the shadow paging method means that database update operations are performed not on the actual database.
This method is performed on the copy.

Here, it is assumed that a copy is created for each page to be updated.

The page(s) of the database entity on which update operations are not performed is called the backup version, and the page(s) on which the entity is cohered and updated is called the current version.

The timing at which update operations are reflected in the entity, that is, the timing at which the current version is made the backup version and the previous backup version is invalidated (this is called a "checkpoint"), determines the efficiency of recovery from system corruption. This is the point at which a certain amount of information has been accumulated to be recorded in a file (referred to as a "log") in order to improve the system's performance. The checkpoint occurs every time the specified amount of log information is accumulated.

[Problems to be Solved by the Invention] In the shadow paging method described above, the page in the update operation is stored in a separate free area on the external storage device (disk, etc.). There was a problem in that page input/output processing, especially when trying to input pages consecutively, caused seek/search processing to occur frequently.

The L1 object of the present invention is to provide a physical clustering method that solves the above-mentioned problems in the conventional physical clustering method and reduces the number of seeks and searches of the external storage device when pages are continuously input.

[Means for solving problems]

The above object of the present invention is to store database information in an external storage device in a database system that employs a shadow paging method, while providing a free area (a plurality of free frames) for each set of physical blocks called a frame. A backup version exists that stores pages and, in update operations, has free space to store pages for the current version. This is achieved by allocating the above frames within a set unit (hereinafter referred to as a "control area").

[Effect]

In a database system adopting a shadow paging method, the present invention stores pages while securing free frames in each control area in advance,
During update processing, by storing the updated page (the above-mentioned "current version") in an empty frame in the control area where the page to be updated exists, scattering is suppressed, and when pages are continuously input. This reduces the number of seek searches of external storage devices.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram of a database system showing an embodiment of the present invention. In the figure, 1 is the central processing unit (
2 is a main storage device, 3 is a channel, 4 is a controller that controls a disk device 5 described below, and 5 is a disk device as an external storage device. The disk device 5 holds a plurality of extents (corresponding to "files") that store database information and a directory that manages database information.

Reference numeral 11 denotes a data access request unit which is a program that issues access requests such as searches and updates to the database. A buffer management unit 12 is a program that holds database information on the main memory, and manages a page input/output buffer of a buffer unit 21, which will be described later. Reference numeral 13 denotes a storage management unit which is a main part of this embodiment, and is a program that performs mapping between physical space and logical database space and manages the usage status of the database. 1
Reference numeral 4 denotes an input/output management section, which is a program that processes data input/output in units of frames between the disk device 5 and the main storage device 2.

Reference numeral 21 denotes a buffer unit, which consists of a page input buffer (group) that holds pages (logical blocks) to be accessed for database information. Reference numeral 22 denotes a directory section, which consists of a plurality of management blocks that hold control information regarding the physical configuration of the database, and the information in the management blocks is accessed by the storage management section 13. As mentioned above, the directory is on disk device 5.
However, at the start of database processing, it is assumed that the directory is loaded onto the main storage device 2 by a request from the storage management section 13 to the input/output management section 14 to make the directory resident in the main memory.

The directory section 22 includes an extent management block 22
A. It is composed of the table management block 22B, page frame mapping block 22G, and control area management block 22D, and has a logical address space (a collection of pages) that mainly stores database information, and a "frame". It has information for mapping with a physical address space that is a collection of physical blocks. Next, each management block within the directory will be explained.

FIGS. 2(A) to 2(D) are diagrams showing details of the directory section 22. As shown in FIG.

FIG. 2(A) shows extent management block(s) 22A.
It has a function of managing extents, which are collections of frames As that store database information. The details of the extent are shown in FIG.

When storing a page, the free space (inside extension 1) is set in units of frame t1, that is, in units of roll area to controller 1.
In order to provide an empty frame (empty frame), the control area is constituted by an aggregate of segments 1-, which is a unit of a plurality of frames, and an empty frame is secured for each segment when page information is stored.

Extent management block(s) 22A shown in FIG.
The size of the control area and segment (number of frames) in the data access request unit 11 requests the storage management unit 13 to set the size (number of frames) of the control area and segment within the storage area, according to the default 1 to value set in advance in the system when securing an extent. be. The number of frames can also be changed by the user using parameters. Extent management block (
The group 22A has a configuration as shown in FIG. 2(A) in order to manage the extents configured as described above.

Next, the table management block 22B has management information for storing and accessing tables (tables of relations) in control areas of the extents. In addition, page frame mapping block (group) 2
2C exists in extent units, 1.2 from the beginning,
3. ..., and the current frame address, which is the address of the frame where the current version of the page is stored, and the address of the frame where the backup version of the page is stored, corresponding to each page. It holds the backup frame address, which is an address, and manages the mapping between logical blocks called pages and physical blocks called frames.

Incidentally, one set of both of the above-mentioned frames is called a map entry, which corresponds to a page number.

The above page numbers are 1.
2, 3. ...and the first page frame of the layout l\・The beginning of the mapping block starts from the last page number of the previous mapping block +1.

Assigned sequentially. Therefore, the page number of the map entry containing the mapping block is calculated as follows.

(Page number of map entry) = (Array number of the block - 1) × (Number of map entries in the block) + Map entry order control area management block (group) 22D in the block has the above extensions 1 to 1. The first control area number is 1'', and numbers are assigned to the control areas sequentially. This corresponds to the array number of the control area management block (group). In addition, the control area management block (group) 22D manages the use and non-use of frames 11 in the control area.In order to identify control area management blocks that store pages of the same table, this management block Contains pointers to the immediately preceding and succeeding control area management plots.

The operation of this embodiment configured as described above will be explained below. The explanation will be based on FIGS. 6(A) to 6(L).

(1) Securing free space when creating a table will be explained based on FIGS. 6(A) to 6(E). Figure 6 (A
) shows the general flow of this process, and Figures 6(B) to (E
) shows the details.

First, we will explain the case of creating a table and storing it in an extent. A table creation request is issued from the data access request unit 11 in the CPUI to the storage management unit 13. At this time, the table ID, the number of free frames per segment, and the ID of the extent storing this table are passed. The storage management unit 13 searches for empty table management blocks (groups) 22B and stores them in the ``table ■[) II, II number of empty frames/segment l-II'' in FIG. 2(B).

Store it in the “extent ID” area.

Next, the data access request unit 11
Pass the table information to and request that it be stored in extensions 1~. The buffer management unit 12 secures a page and allocates it to a page input/output buffer, secures a frame from within the extent, and performs processing to store the page (buffer contents) in the frame. Therefore, first, the storage management unit 13 is called and a page is secured.

The management unit 13 searches the page frame mapping block (group) 22C, and selects the corresponding page where both the current frame address and the backup frame address are "0 (page not secured)". At this time, I is assigned as an assigned flag.
I IF FT Set 11 to the current frame address area. Then, calculate the number of this area from the beginning of the page frame mapping block 22C, and use this as the page number (processes 30.40 to 4).
7).

The buffer management unit 12 allocates the received page number to the unallocated page input/output buffer of the sofa unit 21 (processing 31). Then, table information is set in the page input/output buffer and stored in the extent (processing 32). Therefore, the buffer management unit 12 calls the storage management unit 13 to secure an empty frame (
Processing 50-59). The storage management unit 13 traces the pointer from the control area management block 22D pointed to by the table head control area pointer of the table management block 22B having the table ID, and sets the control flag to 1 (frame reservation OK). ” Search and find the management block.

For the obtained control blocks, excluding frames for free areas, it is determined whether or not free frames (no page numbers are stored) can be secured for each segment 1, and free frames are obtained. More specifically, in order to secure an empty frame from the obtained control block I~roll area management block, one segment size (number of frames)'' from the relevant extension 1~management block 22A, and ``free frame'' from the relevant table management block. Find the number of frames t1/segment'' and calculate the difference between the two as the number of frames/segment that can be secured.
Then, it is determined whether a page number is stored between the beginning of the segment and the number of retrievable frames/segment.

If there is no free frame, the same process is performed for the next segment. If there is an empty frame, set a page number in the area corresponding to frame t1 of the control 1-roll area, and set the control area number and frame number to 1) f page frame mapping block 22C.
Set in the Karen 1 for the corresponding page to area for frame address and area for backup frame. Here, as described above, the controller area number indicates the number of the control area from the beginning of the extension 1-, and corresponds to the array number of the control area management block. Further, the frame tz number indicates the number of the frame from the beginning of the control I to roll area management block.

As mentioned above, after securing frame 11, if all the frames that can be secured in the control area are assigned to the page, the control flag of the control area management block is set to 2 (frames other than those for free space cannot be secured)''. If the first control area pointer for the table in the table management block 22B is 0 (control area not secured), and if the control area pointer of the last chain corresponding to the control area that stores the table information is If the control flag in the area management block is '2' (frames other than those for free space cannot be secured), the table management block 2 corresponding to the table ID
2B, and search for a new free control area management block from the control area management block pointed to by the first control area management block pointer in the extent management block 22A that has information regarding the extent ID. (Group) 22D is searched (control flag is "O") and a vacant controller 1 to roll area for the table is secured (processes 60 to 67).

At this time, the control flag of the secured main management block is set to RI.
Make it 11. The secured main management block is used as the final chain of control area management blocks for the same table, that is, control area blocks 1 to 2 in Figure 2 (D).
As shown in the next control area management block pointer and the previous control area management block pointer in 2D, both areas are con! - Set the array number of the roll area management block. Or, Figure 2 (B
) If the content of the first control area pointer for the table in the table management block 22B is "0", the control area management block 22B is chained to that pointer because the control area/roll area is not secured.

Thereafter, the frame securing process (process 33) described above is performed.

The frame number and the number of the control area are returned to the buffer management unit 12 as the address of the secured frame. The buffer management unit 12 passes the frame address, the address of the page input/output buffer corresponding to this page, and the extent ID to the input/output management unit 14 and requests that the page be outputted (processing 34). Based on the above information, the input/output management unit 14 stores the page in the frame 11 in the corresponding extensions 1 to 1 existing on the disk device 5. The above process is performed every time one page is stored in an extent. This makes it possible to continuously store the pages of the table while providing free space in units of controller 1 to roll areas.

(2) Updating the table Next, we will explain how to store the current version of the page when updating the information in the table.
). FIG. 6(F) shows the general flow of this process, and FIGS. 6(G) to (L) show its details.

First, in order to find the page that stores the information to be updated in the table, the data access request unit 11 requests
A request is issued to the buffer management unit 12 to obtain a page from the table and input page information. The buffer management unit 12 first stores the page input/output buffer 21.
Allocate an empty buffer from within. Then, the table ID is passed to the storage management unit 13 and a request is made to obtain the page number (process 70). Storage management section 1
3 is table management block 2 corresponding to the table ID
2B's top control]--Page numbers are obtained in order from the page number storage area in the top control area management block 22D of the roll area management block 22B and returned to the buffer management section 12.

Next, the buffer management unit 12 passes the table ID and page number to the storage management unit 13, and requests mapping from the page number to a frame address within the extent. The storage management unit 13 searches the table management block 22B corresponding to the passed table ID, obtains the extent ID from within the corresponding management block,
From the extent management block 22A corresponding to the extent ID to the page frame mapping block 22
Find C.

The storage management unit '13 acquires the current frame address and backup frame address corresponding to the corresponding page number of the page frame mapping block 22C determined above, and returns them to the buffer management unit 12. The buffer management unit 12 stores both of the above frame addresses in the secured page input/output buffer, issues a page input request to the input/output management unit 14 based on the current frame address, and transfers the page to the buffer unit 21. , obtained in the secured page input/output buffer (processes 80 to 83
).

If the page includes information to be updated, the data access request unit 11 updates the page information in the page output buffer (processes 71 and 72).

If the information to be updated does not exist in the page, the buffer management unit 12 is requested to input the next page into the page input/output buffer, and the above-described process is performed. That is, duplicate pages are not input (processes 74 and 75).

The data access request unit 11 issues a page output request to the buffer management unit 12 in order to store the updated page in the extent (processing 73). The buffer management unit 12 obtains both the previously stored current frame address and backup frame address from the corresponding page input/output buffer, and compares the two addresses.

If the two addresses are not equal, the current frame address is specified and a request is made to the input/output management unit 14 to output the page already stored in the page input/output buffer (processing 94). Furthermore, if the above two addresses are the same, it is necessary to allocate a new frame in order to store the 1) current version page (updated page).

Therefore, from the buffer management unit 12 to the storage management unit 1
The table ID, page number, and backup frame address are passed to No. 3 to request that the frame be secured (processes 90 to 92). The storage management unit 13 obtains the controller area number and frame number as the backup frame address, and also obtains the corresponding table management block 22I3 from the table ID as described above.
The corresponding extent management block 22A is determined from the extent ID held in the block, and the number of frames in the control area and the number of frames in the segment are obtained.

From this information, calculate the segment 1 number in which the backup version page exists, and in order to secure an empty frame within the segment, start from the first frame of the segment to the last frame (first frame number child segment size) The page number storage area in the control area management block 22D corresponding to
(i.e., empty frame zs for which no page number is set)" (processes 100 to 10
4).

If the page number storage area is 0'', a page number is set there.Thereby, it is possible to secure a frame for the Karen 1-version page in the segment.

Next, the number of the page number storage area from the top page number storage area of the control 1 to roll area management block 22D is calculated and used as the frame number. Then, on the page that requested frame reservation, the page frame for the corresponding extent is
In the area of the current frame address corresponding to that page in the mapping block 22C, the number of the secured frame and the control area number where the secured frame t1 exists are processed 105 to 107), and then the buffer The secured current frame address is returned to the management unit 12 (process 108).

The buffer management unit 12 passes the address of the page input/output buffer storing the current frame address and the updated page information to the input/output management unit 14, and issues an output request to the extent, thereby updating the page information. The page is stored in a designated frame within the second stent (process 93).

If there is no free frame in the segment, free frames (including frames for free space) in other segments in the control area where the backup version page exists are secured (processes 109 to 114).
).

The above processing is performed every time a page is updated.

According to the above embodiment, the updated page can be stored near the frame in which the unupdated page is stored, and the number of seeks and searches of the external storage device when accessing the page can be reduced. This has the effect of making it possible to reduce the time occupied by the external storage device and the input/output load.

Next, as another embodiment of the present invention, an example will be shown in which, when re-editing the database, the size of the free frame is dynamically changed and secured according to the number of updates (distribution) of the page(s). .

The difference in structure between this embodiment and the first embodiment described above is as follows.

The present embodiment is configured to have the following additional functions.

That is, (1) The number of table updates is stored in the table management block 22B in the directory section 22 as one of the statistical information for dynamically changing the amount of free space in the control area when reorganizing the table. have an area for counting.

(2) A method of changing the free space in units of segments that make up the control area in order to grasp the update status of pages stored in the control area and dynamically change the amount of free space in the control area when reorganizing. and 0 "control area management block 22
In D, there is provided an area corresponding to each segment to count the number of updates of a page updated within the corresponding segment pair.6 Below, the operation of this embodiment having the above-mentioned characteristics will be explained. Note that since most of the operations of this embodiment are the same as those of the previous embodiment, only the parts that are different from the previous embodiment will be explained in the following description.

FIGS. 4A and 4B show detailed configurations of the table management blocks in the pointer 1 to 22 parts and the control area management block, which are the features of this embodiment described above.

That is, FIG. 4(A) shows a table management block 22E corresponding to the table management block 22B in the previous embodiment, and the difference between the two is that the table management block 22E according to the present embodiment is on the top. It has the above-mentioned table update count area and a table reorganization head control area management block pointer, which will be described later.

Further, FIG. 4(B) shows a control area management block 22F corresponding to the control area management block 22D in the previous embodiment, and the difference between the two is that the control area management block 22F according to the present embodiment is The main feature is that it has the segment-compatible management area mentioned above.

(1) Securing free space when creating a table This operation is exactly the same as the operation shown in the previous embodiment.

(2) Updating a table Here, a method for storing pages of the current version when updating information in a table and a method for acquiring statistical information for table reorganization will be explained.

First, in order to find the page that stores the information to be updated in the table, the data access request unit 11 requests
A request is issued to the buffer management unit 12 to obtain a page from the table and input page information. The buffer management unit 12 passes the table ID to the storage management unit 13 and requests it to obtain the page number. The process up to this point is the same as the previous embodiment.

The storage management unit 13 adds 1'' to the table update count area in the table management block 22E for table reorganization in order to count the number of table updates as statistical information.

Page numbers are sequentially obtained from the page number storage area in the control area management block 22F pointed to by the first control 1-roll area management block pointer of the table management block 22E corresponding to the table ID, and returned to the buffer management unit 12.

Next, the operations shown in page 16, line 17 of this specification to page 20, line 11 [1] are sequentially performed. In addition, in this description, the table management block 22B, the same 22E, and the control 1-roll area management block 22D.
shall be read as 22F.

In addition, when performing the controller 1 roll area number set operation, at the same time, in order to obtain statistical values to reserve free space when reorganizing the table, the page number of the current version is calculated from the segment number where the page of the current version exists. , rt 1 u is added to the intra-segment update page count area in the corresponding management area of segment 1 to the corresponding management area.

Next, the operations shown from line 12 on page 20 to line 5 on page 21 of this specification are performed.

(3) Reorganization of tables Next, table reorganization will be explained.

When tables are updated or added, free space in the control area is quickly used up, and if new control areas are allocated more frequently, the database system automatically detects the need to reorganize tables. Understand,
Reorganize the table. The same process is also performed when a table reorganization request is issued by a user.

When reorganizing a table, first, the data access requesting unit 11 passes the table ID to the storage management unit 13 to request that all controllers 1 storing table information reorganize their roll areas.

The storage management unit 13 obtains the table management block 22E corresponding to the above-mentioned table ID in the directory unit 22, and uses the leading control area management block pointer for the table in the table management block 22E to find the leading control area management block of the table. 1().

Next, the storage management unit 13 controls the control area from the control area corresponding to the first control area management block.
The free space (free frame) that is predicted to be necessary for each segment is calculated, and the page information is transferred while providing the calculated free space to the newly secured control area.

As a method for calculating the estimated necessary free space for each segment, for example, one of the following methods can be used.

(1) A method of determining the maximum number of updated pages for each segment in table update processing that occurs during the period before table reorganization, and securing free space for the maximum number of pages. In this case, each time the table is updated, the maximum number of page updates per segment is acquired as statistical information.

(2) A method of determining the average number of updated pages for each segment and securing free space for that number of pages.

Here, the explanation will be continued assuming that the latter method of securing free space for the average number of pages is adopted.

The average number of pages in this method can be calculated by dividing the total number of pages updated within a given segment by the number of times the table was updated within the same period. less than,
The calculation formula is shown below.

(Number of free frames to be secured) Number of times the table has been updated In the case of the above-mentioned method of securing free space for the maximum number of updated pages, (Number of free frames to be secured) = Number of times the table has been updated within a certain period of time. This is the maximum number of updated pages within the segment.

As a value necessary for the former calculation formula, the number of times the table has been updated is stored in the table management block 22 of the table ID.
Obtain the number of updates of the table in E from Callan 1-area,
The number of updated pages in the segment is obtained from the intra-segment updated page count area (see FIG. 4) in the segment 1-corresponding management area in the control area management block 22F for the table (processing 12).
0-123).

It is assumed that the update page count number in segment 1 and the number of times the table has been updated are reset when the control area of the table is reorganized. This reset 1- is performed by the storage management unit 1:3.

Next, the storage management unit 13 secures a new control area to which the pages in the segment are to be transferred.

First, in order to determine whether or not the new controller 1~roll area is secured, it is determined that the reorganization head controller 1~roll area management block pointer in the table management block 22E corresponding to the table ID is II OII. Check whether or not. In the case of rr Ou, a management block whose control flag of the control area management block 22F is 0 (control area empty) is searched, and an empty control area management block is secured.

At this time, set the control flag of the main management block secured to “1 (
Frame reservation OK)" and set the start address of this management block in the reorganization start control area management block pointer area of the table management block corresponding to this table ID (processes 124, 127, 1).
28).

If the control area management block pointer for reorganization is not "0'', it means that the control area has already been secured, and the next control area management block pointer of the first control area management block is followed, and the control flag is obtains the control area management block of II I 11 (process 125).

Furthermore, in order to move the pages within the segment of the control area management block to be reorganized, the control area management block that has been secured or found,
Secure new segment 1-.

First, in order to obtain the first frame of a new segment, the segment corresponding management area is set to 0 (unallocated segment 1-) from the beginning of the control 1 to roll area management block 22F.
', and obtain the last frame number stored in the segment from the segment corresponding management area one before this.

This frame number +1 is the first frame number of the newly secured segment. This is set in the area of the first frame number stored in the segment (see Figure 5) of the obtained segment correspondence management area (process 132.13).
:3).

The pages within the segment targeted for reorganization are then
In order to store data in segments 1 to 1 secured in the new controller 1-roll area, the storage management unit 13 stores the data in the buffer management unit 1.
2, frame numbers (plurality) in which page numbers are set in the frame management area corresponding to the segment to be reorganized and the number of the control area containing the segment.

It passes the extent ID and issues a request (process 134) to input all pages stored in the segment to the page input/output buffer of the buffer unit 21.

The buffer management unit 12 first secures page input/output buffers for the number of input pages (number of frames), and transfers the received extension 1 to ID, control area number, and frame number (plurality) to the input/output management unit 14. and requests page input within the corresponding frame.

The input/output management unit 14 uses the external storage device 5 based on the above information.
Acquires a page from the frame in the corresponding extent that exists above and stores it in the page input/output buffer.

The above process is performed for each page.

The buffer management unit 12 stores pages for all frames,
It receives from the input/output management section 14 that the page has been stored in the page turnout sofa, and reports it to the storage management section 13.

Next, the storage management unit 13 passes the page numbers to the buffer management unit 12 so that the pages in the page input/output buffer are stored in the newly secured segment I in ascending order of page numbers. request.

Therefore, first, the storage management unit 13 obtains the previously obtained in-segment storage first frame number from the segment support management unit ``rear'' corresponding to the new segment in which the page is to be stored, and sends the page to the buffer management unit 12. A request is made to store the page with the lowest page number in the crowd cover rough γ in the frame with the first frame number.

The buffer management unit 12 receives from the storage management unit 13 the first frame number, the control area number where the frame exists, and the ID of extension 1- where the control area exists, and stores the page with the lowest page number. The input/output management unit 14 is requested to output the page cover sofa in a specified frame.

Based on the above information, the input/output management unit 14 stores the external storage device 5-
The page is output to a frame within the corresponding extent existing in H.

After outputting the page, the storage management unit 13 outputs the page frame mapping block 22C corresponding to the extent.
In the current frame address and backup frame 11 address areas corresponding to the output page number of , the control area number of the page output this time and
The frame number is set (processes 135 to 142).

Similarly, the process of outputting a page into a segment and changing the current address and backup address is performed in ascending order of page numbers in the page input/output buffer while processing frame numbers +1.

As a result, the pages in the segment to be reorganized are stored in the newly allocated segment in descending order of size.

Next, in order to find the final frame number when free space (free frame) is set in the new segment, in the newly allocated segment, add the previously calculated number to the frame number that stores the last page. The number of frames to be secured in the segment pair is added and the value is set to the last frame number stored in segment I of the management area for segment 1 corresponding to the segment (see FIG. 5).

The above is a reorganization process for one segment.

Perform these processes in the same way for the subsequent segments 1~, and once all pages of segment 1~ of this controller 1-roll area have been transferred, transfer the controller 1-roll area management block 22F corresponding to the roll area to this controller 1. next con 1 in
- From the roll area management block pointer, the next controller
- Find the roll area management block and similarly process the next control area segment.

If in the control 1-roll area (for reorganization).

If enough allocatable frames cannot be secured for the segment, set the control flag in the control 1-roll area management block corresponding to the control area (for reorganization) to l.
(2H) Set (frames cannot be secured except for free space), secure a new control area as in 1., and secure a segment in that control area.

After the reorganization process for segment 1- of all control areas in this table is completed, the corresponding table management block 2 is deleted in order to erase the control area management block before reorganization.
While tracing the chain from the control area management block pointed to by the first control i-roll area management block pointer for the table in 2E, set the control flags in sequence.
(empty state)" and erase other areas in the block. Then, change the value of the reorganization start control area management block pointer in the I core table management block to the start control area management block pointer for the table. The area of the management block pointer for reorganization is deleted (processes 146 to 148).

According to the above embodiment, the updated page can be stored near the frame in which the unupdated page is stored, and the number of seeks and searches of the external storage device when accessing the page can be reduced. This not only has the effect of reducing the time occupied by the external storage device and the input/output load, but also secures free space (free frame ZS) corresponding to the page update frequency when reorganizing tables. There is also the effect that it can be done.

Therefore, compared to the method shown in the first embodiment in which a certain amount of free space is secured in advance, this method is more effective in preventing pages stored in the external storage device from becoming discontinuous. Another effect is that the page storage area can be saved by reducing the amount of free space in the storage area for pages that are updated less frequently.

In the above embodiment, when dynamically changing the amount of free space in the control 1-roll area, a method was explained in which the free space is changed in segment units. A method of changing on an area basis is also possible.

In this case, for example, the controllers 1 to 1 shown in FIG.
In the roll area management block 22F, a control 1-roll area update page count area is provided instead of the segment corresponding management area group (see Figure 5), and here,
The number of updated pages for each control area may be set to 1.

If configured as above, when reorganizing the table,
This has the effect that a free area corresponding to the page update frequency can be secured with a relatively small storage capacity.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to store an updated page near the frame in which the page before the update is stored, and it is also possible to・The number of searches can be reduced, and
This has the effect that the time occupied by the external storage device and the input/output load can be reduced.

Further, as shown in the second embodiment, when the amount of free space is dynamically changed according to the number of updates, there is an effect that even more efficient management becomes possible.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a database system t1 showing an embodiment of the present invention, FIGS. (A)
Figures 4(A) and 4(B) are diagrams showing details of the extension 1 management block (group) shown in FIG. FIG. 5 is a diagram showing details of the segment corresponding management area shown in FIG. 4(B), and FIGS. 6(A) to (L) are processing flowcharts showing the operation of the embodiment. 1: CI) U, 11: Data access request unit, 1
2: Buffer management section, 13: Storage management section, 14:
Input/output management unit, 2: Main storage device, 21: Page input/output buffer, 22: Tiref 1 edge section, 22A: Extent management block, 22B, 22E: Table management block, 22C: Page frame mapping block, 22D, 22F: Roll area management block to controller 1, 5: Disk device. Figure 1 Figure 2 Figure 2A 2B Figure 2 Figure 2 Figure 3 Figure 5 Figure 6 Figure 4 (B) 22F Figure 6 Figure 03) Figure 6 fc) Figure 6) Figure 6 CF) Figure 6 (G) Figure 6 ■

Claims (1)

[Claims] 1. A database that adopts a shadow paging method.
When storing pages on an external storage device in a computer system in which the system operates, an empty frame is provided for each set of frames that store pages, and during update processing, an empty frame is provided near the frame in which the page to be updated is stored. To,
A physical clustering method characterized by storing updated pages. 2. Database that uses shadow paging method
When storing pages on an external storage device in a computer system in which the system operates, an empty frame is provided for each set of frames that store pages, and during update processing, an empty frame is provided near the frame in which the page to be updated is stored. To,
At the same time as storing the updated page, the number of updates is counted for each set of frames in which the page to be updated exists, and when the database is re-edited, the number of free frames provided for each set of frames is calculated by updating the A physical clustering method that dynamically changes according to the number of times.