System of compressing the tail of a sparse log stream of a multisystem environment

• US 6,125,393 A
• Filed: 03/28/1997
• Issued: 09/26/2000
• 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): Luu, Le Hien
• Assistant Examiner(s): YUAN, ALMARI ROMERO
• Application Number:
  US08/827,559
• Time in Patent Office: 1,278 Days
• Field of Search: 379/106.01, 379/106.03, 379/106.02, 379/106.06, 340/853.2, 702/187, 709/224, 709/231, 711/112, 711/114, 707/206, 707/202, 707/101
• US Class Current: 709/224
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/3476 Data logging G06F11/14, G06F11/2205 take precedence
• CPC Class Codes: G06F 11/348 Circuit details, i.e. tracer hardware
• 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 system of compressing a multisystem log stream of a multisystem environment, said system comprising:

means for 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;

means for 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;

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

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

2. The system 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 system 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 system of claim 3, wherein said means for selecting comprises means for 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 system of claim 4, wherein said means for using comprises means for removing said one or more entries older than said deletion position.

6. The system of claim 1, further comprising:

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

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

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

said first system being adapted to rewrite one or more entries of said multisystem log stream owned by said second system to one or more other locations; and

means for setting said second position to reflect said rewriting.

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

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

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

11. The system of claim 1, further comprising:

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

means for setting said first position to reflect said rewriting.

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

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