Tail compression of a sparse log stream of a multisystem environment

• US 5,999,935 A
• Filed: 03/28/1997
• Issued: 12/07/1999
• Est. Priority Date: 03/28/1997
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Haggar, Jeffrey Douglas, Greenspan, Steven Jay, Clark, Carl Edward, Sutherland, Danny Ray
• Primary Examiner(s): Kulik, Paul V.
• Application Number:
  US08/827,214
• Time in Patent Office: 984 Days
• Field of Search: 707/101, 707/202
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A multisystem log stream of a multisystem environment is compressed. The oldest record needed for each system that can write or delete entries from the multisystem log stream is tracked, and that information is used in compression of the log stream. The block ids associated with those oldest records are maintained within a vector, and when the vector is updated, a determination is made as to whether the entry in the vector that it replaced previously contained the lowest block id in the vector. If so, all the records having block ids lower than the new lowest block id in the vector are deleted.

Claims

1. A method of compressing a multisystem log stream of a multisystem environment, said method comprising:

determining for a first system of said multisystem environment a first position within said multisystem log stream from which one or more entries of said multisystem log stream can be deleted;

determining for a second system of said multisystem environment a second position within said multisystem log stream from which one or more entries of said multisystem log stream can be deleted;

selecting from said first position and said second position a deletion position within said multisystem log stream; and

using said deletion position to remove one or more entries from said multisystem log stream.

2. The method of claim 1, wherein said first position comprises a first block id, said first block id representing the oldest entry within said multisystem log stream that is wanted for said first system.

3. The method of claim 2, wherein said second position comprises a second block id, said second block id representing the oldest entry within said multisystem log stream that is wanted for said second system.

4. The method of claim 3, wherein said selecting comprises comparing the first block id and the second block id to determine therefrom the oldest entry to be kept within said multisystem log stream, said oldest entry corresponding to the deletion position.

5. The method of claim 4, wherein said using comprises removing said one or more entries older than said deletion position.

6. The method of claim 1, further comprising:

logically deleting one or more entries owned by said first system from said multisystem log stream; and

updating said first position, when said logically deleting causes a change in said first position.

7. The method of claim 1, wherein said second system is an inactive system, and said method further comprises:

rewriting, by said first system, one or more entries of said multisystem log stream owned by said second system to one or more other locations; and

setting said second position to reflect said rewriting.

8. The method of claim 7, wherein said one or more other locations is at or near a head of said multisystem log stream.

9. The method of claim 7, wherein at least one of said one or more other locations is within another log stream.

10. The method of claim 7, wherein said setting comprises setting said second position to a highest block id of said multisystem log stream.

11. The method of claim 1, further comprising:

rewriting one or more active entries of said multisystem log stream owned by said first system to one or more other locations; and

setting said first position to reflect said rewriting.

12. The method of claim 11, wherein said one or more other locations is at or near a head of said multisystem log stream.

13. The method of claim 11, wherein at least one of said one or more other locations is within another log stream.

14. An article of manufacture comprising:

a computer useable medium having computer readable program code means embodied therein for causing the compressing of a log stream, the computer readable program code means in said article of manufacture comprising;

computer readable program code means for causing a computer to effect determining for a first system of said multisystem environment a first position within said multisystem log stream from which one or more entries of said multisystem log stream can be deleted;

computer readable program code means for causing a computer to effect determining for a second system of said multisystem environment a second position within said multisystem log stream from which one or more entries of said multisystem log stream can be deleted;

computer readable program code means for causing a computer to effect selecting from said first position and said second position a deletion position within said multisystem log stream; and

computer readable program code means for causing a computer to effect using said deletion position to remove one or more entries from said multisystem log stream.

15. The article of manufacture of claim 14, wherein said first position comprises a first block id, said first block id representing the oldest entry within said multisystem log stream that is wanted for said first system.

16. The article of manufacture of claim 15, wherein said second position comprises a second block id, said second block id representing the oldest entry within said multisystem log stream that is wanted for said second system.

17. The article of manufacture of claim 16, wherein said computer readable program code means for causing a computer to effect selecting comprises computer readable program code means for causing a computer to effect comparing the first block id and the second block id to determine therefrom the oldest entry to be kept within said multisystem log stream, said oldest entry corresponding to the deletion position.

18. The article of manufacture of claim 17, wherein said computer readable program code means for causing a computer to effect using comprises computer readable program code means for causing a computer to effect removing said one or more entries older than said deletion position.

19. The article of manufacture of claim 14, further comprising:

computer readable program code means for causing a computer to effect logically deleting one or more entries owned by said first system from said multisystem log stream; and

computer readable program code means for causing a computer to effect updating said first position, when said logically deleting causes a change in said first position.

20. The article of manufacture of claim 14, wherein said second system is an inactive system, and said computer readable program code means in said article of manufacture further comprises:

computer readable program code means for causing a computer to effect rewriting, by said first system, one or more entries of said multisystem log stream owned by said second system to one or more other locations; and

computer readable program code means for causing a computer to effect setting said second position to reflect said rewriting.

21. The article of manufacture of claim 20, wherein said one or more other locations is at or near a head of said multisystem log stream.

22. The article of manufacture of claim 20, wherein at least one of said one or more other locations is within another log stream.

23. The article of manufacture of claim 20, wherein said computer readable program code means for causing a computer to effect setting comprises computer readable program code means for causing a computer to effect setting said second position to a highest block id of said multisystem log stream.

24. The article of manufacture of claim 14, further comprising:

computer readable program code means for causing a computer to effect rewriting one or more active entries of said multisystem log stream owned by said first system to one or more other locations; and

computer readable program code means for causing a computer to effect setting said first position to reflect said rewriting.

25. The article of manufacture of claim 24, wherein said one or more other locations is at or near a head of said multisystem log stream.

26. The article of manufacture of claim 24, wherein at least one of said one or more other locations is within another log stream.