Cache management method for storage device

• US 6,944,711 B2
• Filed: 08/25/2003
• Issued: 09/13/2005
• Est. Priority Date: 03/28/2003
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Mogi, Kazuhiko, Nishikawa, Norifumi, Eguchi, Yoshiaki
• Primary Examiner(s): NGUYEN, THAN VINH
• Application Number:
  US10/646,699
• Publication Number:
  US 20040193803A1
• Time in Patent Office: 750 Days
• Field of Search: 711/118, 711/128, 711/129, 711/136, 711/170, 711/173, 707/200, 707/205, 707/1, 707/3
• US Class Current: 711/113
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 12/0873 Mapping of cache memory to specific storage devices or parts thereof
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 2212/282 Partitioned cache
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A cache management method disclosed herein enables optimal cache space settings to be provided on a storage device in a computer system where database management systems (DBMSs) run. Through the disclosed method, cache space partitions to be used per data set are set, based on information about processes to be executed by the DBMSs, which is given as design information. For example, based on estimated rerun time of processes required after DBMS abnormal termination, cache space is adjusted to serve the needs of logs to be output from the DBMS. In another example, initial cache space allocations for table and index data is optimized, based on process types and approximate access characteristics of data. In yet another example, from a combination of results of pre-analysis of processes and cache operating statistics information, a change in process execution time by cache space tuning is estimated and a cache effect is enhanced.

Claims

1. A device for setl:

ing cache space in a data processing system including a computer on which a database management system runs, a storage device which includes a cache and stores data in databases which the database management system manages, and an administrative device which manages the computer and the storage device, wherein the computer, the storage device, and the administrative device are interconnected via a network, the device comprising;

means for acquiring information about database function process details to be executed by the database management system;

means for acquiring information about data mapping from the computer and the storage device;

means for creating planned cache space settings, using the acquired information about said database function process details and about said data mapping; and

means for directing the storage device to activate cache space settings according to the planned cache space settings.

2. The device according to claim 1, wherein all the means are corresponding functions realized by a system management program provided on the administrative device.

3. The device according to claim 1, further comprising:

storage control means connected to the computer and the storage device and which controls data transfer between both;

mapping means for defining mapping to data on the databases in the storage control means; and

means for acquiring information about mapping of data on the databases from the mapping means.

4. The device according to claim 1, wherein all the means are functions realized in the computer, the storage device, or the storage control means.

5. The device according to claim 1, wherein the administrative device includes means for acquiring, as information about the database function process details to be executed by the database management system, SQL statements to be executed for the process and an expected count of execution of the SQL statements.

6. The device according to claim 5, wherein the administrative device includes means for acquiring, as further information about the database function process details to be executed by the database management system, a ratio of execution of the process.

7. The device according to claim 2, wherein:

the administrative device includes;

means for further acquiring, as the acquired information, information about performance of rerun of processes after abnormal termination of the database management system and information about rerun time settings after abnormal termination of the database management system; and

means for creating planned cache space settings for logs which the database management system outputs as the planned cache space settings on the storage device.

8. The device according to claim 2, wherein:

the administrative device includes;

means for further acquiring, as information about the database function process details to be executed by the database management system, information about size of data to be accessed during the process execution, information about distribution of access, to data to be accessed during the process execution, and information about cache space available in the database management system and the storage device, and

means for creating planned cache space settings for tables and indexes which are data which the database management system manages as the planned cache space settings on the storage device.

9. The device according to claim 5, wherein:

the storage device includes means for acquiring operating statistics information about access to the cache and the database management system includes means for acquiring operating statistics information about wait occurrences when accessing tables and indexes which the database management system manages; and

the administrative device includes means for further acquiring, as the acquired information, the cache access related operating statistics information as well as the operating statistics information about wait occurrences when accessing the tables and indexes, and means for creating planned change to cache space settings for tables and indexes which the database management system manages as the planned cache space settings on the storage device.

10. The device according to claim 1, wherein the administrative device includes means for acquiring, as information about the database function process details to be executed by the database management system, the number of expected data pages to access in tables and indexes which are data which the database management system manages during the process.

11. The device according to claim 10, wherein:

the administrative device includes;

means for further acquiring, as information about the database function process details to be executed by the database management system, a ratio of execution of the process, information about size of data to be accessed during the process execution, information about distribution of access to data to be accessed during the process execution, and information about cache space available in the database management system and the storage device; and

means for creating planned cache apace settings for tables and indexes which are data which the database management system manages as the planned cache space settings on the storage device.

12. The device according to claim 10, wherein:

the storage device includes means for acquiring operating statistics information about access to the cache and the database management system includes means for acquiring operating statistics information about wait occurrences when accessing tables and indexes which the database management system manages; and

the administrative device further includes means for acquiring, as the acquired information, the cache access related operating statistics information as well as the operating statistics information about wait occurrences when accessing the tables and indexes, and means for creating planned change to cache space settings for tables and indexes which the database management system manages.

13. The device according to claim 1, wherein the means for acquiring information acquire data mapping information from the database management system, a file system, and a volume manager included on the computer.

14. The device according to claim 1, wherein:

the administrative device includes;

means for further acquiring, as the acquired information, information about;

performance of rerun of processes after abnormal termination of the database management system and information about rex-un time settings after abnormal termination of the database management system, and

means for creating planned cache space settings for logs which the database management system outputs as the planned cache space settings on the storage device.

15. The device according to claim 1, wherein:

the administrative device includes;

means for further acquiring, as information about the database function process details to be executed by the database management system, information about size of data to be accessed during the process execution, information about distribution of access to data to be accessed during the process execution, and information about cache apace available in the database management system and the storage devices and

means for creating planned cache space settings for tables and indexes which are data which the database management system manages as the planned cache space settings on the storage device.

16. The device according to claim 1, wherein:

the storage device includes means for acquiring operating statistics information about access to the cache and the database management system includes means for acquiring operating statistics information about wait occurrences when accessing tables and indexes which the database management system manages; and

the administrative device includes means for further acquiring, as the acquired information, the cache access related operating statistics information as well as the operating statistics information about wait occurrences when accessing the tables and indexes, and means for creating planned change to cache space settings for tables and indexes which the database management system manages as the planned cache space settings on the storage device.

17. The device according to claim 1, wherein:

the administrative device includes;

means for further acquiring, as information about the database function process details to be executed by the database management system, a ratio of execution of the process, information about size of data to be accessed during the process execution, information about distribution of access to data to be accessed during the process execution, and information about cache space available in the database management system and the storage device; and

means for creating planned cache apace settings for tables and indexes which are data which the database management system manages as the planned cache space settings on the storage device.

18. The device according to claim 1, wherein:

the storage device includes means for acquiring operating statistics information about access to the cache and the database management system includes means for acquiring operating statistics information about wait occurrences when accessing tables arid indexes which the database management system manages; and

the administrative device further includes means for acquiring, as the acquired information, the cache access related operating statistics information as well as the operating statistics information about wait occurrences when accessing the tables and indexes, arid means for creating planned change to cache space settings for tables and indexes which the database management system manages.

19. A computer-executable program embodied on a computer-readable medium for setting cache space, which is executed in a data processing system comprising a computer on which a database management system runs and a storage device, which includes databases on which data is stored under management of the database management system end a data cache which temporarily retains data from the databases, the computer-executable program comprising:

means for acquiring information about database function process details to be executed by the database management system;

means for acquiring information about data mapping from the computer and the storage device;

means for creating planned cache space settings, using the acquired information said database function process details and about said data mapping; and

means for directing the storage device to activate cache space settings according to the planned cache space settings.

20. A method for managing a data cache in a data processing system including a storage device which includes disk storage units on which data is stored and a data cache which temporarily retains at least a part of the data that is stored on the disk storage units, a computer on which a database management system (DBMS) program which manages storing data to the storage device is run, the computer carrying out data processing, and an administrative device provided with a system management program for supervising and managing the computer and the storage device, wherein the storage device, the computer, arid the administrative device are interconnected via a network,

the method comprising the steps of:

determining a maximum number of processes that can be executed during a rerun, referring to process design information;

obtaining SQL statements to do INSERT/UPDATE from the processes and expected repetition rates of the SQL statements;

determining maximum data size of logs to be output by the SQL statement to do UPDATE/INSERT;

calculating log data size per process from the maximum data size of logs;

estimating log size required, based on the log data size per process and the maximum number of processes that can be executed during a rerun;

setting cache space as much as or more than the log size required during a rerun to reside on the data cache; and

allocating cache storage areas according to cache space settings thus determined.

21. The method for managing a data cache according to claim 20, wherein, if a logical disk storage unit to which logs should be stored belongs to a free cache group, the free cache group is defined and a part or all of the cache space as much as or more than the log size required during a rerun is allocated to the cache group.

22. A method for managing a data cache in a data processing system including a storage device which includes disk storage units on which data is stored and a data cache which temporarily retains at least a part of the data that is stored en the disk storage units, a computer which includes a cache and on which a database management system (DBMS) program which manages storing data to the storage device is run, and an administrative device provided with a system management program for supervising and managing the computer and the storage device,

the method comprising the steps of:

allocating equal amounts of space in the cache of the DBMS and the data cache of the storage device to all data structures;

specifying a cache effect function for each data structure and allocating space in the cache of the DBMS to each data structure, using the cache effect function;

specifying the cache effect function and allocating space in the data cache to each data structure, using the cache effect functions and

directing one of the DBMS and the storage device to activate cache space allocations thus determined.

23. The method of claim 22, further comprising;

determining the data quantity of data pages to store data except leaf nodes for each data structure and allocating space available in the cache of the DBMS as much as the data quantity thus determined to each data structure; and

determining the data quantity of data pages to store leaf nodes and allocating space available in the data cache of the storage device as much as the data quantity thus determined and space available in the cache of the DBMS by a predetermined ratio to the corresponding data cache space to each data structure.

24. The method of claim 22, further comprising the steps of:

in the data processing system,

virtualizing the disk storage units into a plurality of logical disk storage units;

dividing the whole data cache space into groups having storage areas in Units of the logical disk storage units;

identifying a logical disk storage unit to which logs should be stored and a cache group under which the logical dick storage unit falls from mapping information; and

directing the storage device to activate the cache group thus identified and cache space settings of storage areas for the cache group.

25. The method of claim 22, wherein said data structures include table and index data.

26. The method of claim 22, wherein the DBMS manages its own cache and the data cache of the storage device, regarding the caches as a single cache entity.

27. The method of claim 22, further comprising the steps of:

issuing a caching request from the DBMS to the storage device to cache data from a storage location within the storage device to the data cache; and

issuing a write request with the caching request to cache data which has just been written to the cache within the DBMS to the data cache within the storage device.

28. A method for optimum caching management for data cache in a data processing system including a storage device which includes disk storage units on which data is stored and a data cache which temporarily retains at least a part of the data that is stored on the disk storage units, a computer on which a database management system (DBMS) program which manages storing data to the storage device is run, and an administrative device provided with a system management program for supervising and managing the computer and the storage device,

the method for optimum caching management for the data cache comprising the steps of:

checking statistics about a count of occurrences of wait when accessing data pages of data structures within the DBMS;

identifying processes involving access to a data structure for which it has been determined that wait has occurred with high frequency and obtaining the number of expected data pagan to access in the data structure;

checking for a process which takes long execution time and accessed many times the data structure for which wait has occurred with high frequency among the processes involving access to the data structure;

tailoring cache allocations to enhance a cache hit rate of the data to be accessed during the process execution to shorten the execution time of the process; and

directing the storage device to activate change to data cache allocations according to tailored cache allocations.

29. The method for optimum management for data cache according to claim 28, further comprising the step of tailoring cache allocations to enhance the cache hit rate of the data to be accessed during the execution of the processes and reduce the total sum of execution time of the processes as a whole.