System of compressing the tail of a sparse log stream of a computer system

• US 5,956,735 A
• Filed: 03/28/1997
• Issued: 09/21/1999
• Est. Priority Date: 03/28/1997
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Greenspan, Steven Jay, Clark, Carl Edward
• Primary Examiner(s): Ellis, Richard L.
• Application Number:
  US08/827,558
• Time in Patent Office: 907 Days
• Field of Search: 711/114, 707/202, 707/205, 707/206, 395/183.21, 395/182.04, 714/45, 714/6
• US Class Current: N/A
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27
• CPC Class Codes: G06F 17/40 Data acquisition and logging for input to computer G06F3/00
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99957 Garbage collection

Abstract

When a log stream has a determined amount of reusable space, the log stream is compressed in order to free up the reusable space. Compression of the log stream includes rewriting one or more active entries located at one or more positions of the log stream to one or more other locations, either within the same log stream or on another log stream. Thereafter, the rewritten entries are deleted from their previous positions within the log stream. Additionally, one or more logically deleted entries of the log stream is removed from the log stream. The resulting log stream is a compressed log stream.

Claims

1. A log stream compression system comprising:

a compressible set of entries, said compressible set comprising a plurality of entries of said log stream, said plurality of entries comprising one or more, but less than all, active entries of said log stream; and

a system adapted to rewrite one or more active entries of said compressible set, located at one or more first locations of said log stream, to one or more second locations, the rewriting occurring when said log stream includes a determined amount of reusable space.

2. The log stream compression system of claim 1, wherein said system is adapted to remove said one or more rewritten entries from said one or more first locations, and adapted to remove one or more logically deleted entries of said compressible set from said log stream.

3. The log stream compression system of claim 1, wherein said one or more first locations is at or near a tail of said log stream, and said one or more second locations is at or near a head of said log stream.

4. The log stream compression system of claim 1, wherein at least one of said one or more second locations is within another log stream.

5. The log stream compression system of claim 1, wherein said predefined amount of reusable space is based on a count of logically deleted entries of said log stream.

6. The log stream compression system of claim 1, further comprising means for defining said compressible set.

7. The log stream compression system of claim 6, wherein said means for defining comprises:

means for locating a logically deleted entry of said log stream; and

means for selecting one or more entries located between said logically deleted entry and another entry of said log stream, inclusive of said logically deleted entry and said another entry.

8. The log stream compression system of claim 7, wherein said another entry is an entry at said tail of said log stream.

9. The log stream compression system of claim 7, wherein said means for locating comprises means for searching a first queue to find said logically deleted entry, said first queue comprising a plurality of elements representative of a plurality of entries of said log stream.

10. The log stream compression system of claim 9, wherein said means for selecting comprises:

means for deleting from said first queue one or more elements representative of said one or more entries located between said logically deleted entry and said another entry, inclusive of said logically deleted entry and said another entry; and

means for inserting said one or more elements on a second queue, said one or more elements on said second queue corresponding to said compressible set.

11. A log stream compression system comprising:

a deletion point within said log stream; and

a system adapted to rewrite one or more active entries of one or more first positions of said log stream to one or more second positions of said log stream, said one or more active entries being located in a compression zone, said compression zone being between said deletion point and another point of said log stream, inclusive of said deletion point and said another point, wherein one or more active entries not included within said compression zone are not rewritten.

12. The log stream compression system of claim 11, wherein said one or more first positions is at or near a tail of said log stream and said one or more second positions is at or near a head of said log stream.

13. The log stream compression system of claim 11, wherein said deletion point comprises a last entry within said log stream to be logically deleted.

14. The log stream compression system of claim 11, wherein said system is further adapted to perform said compressing when a count of logically deleted entries of said log stream has reached a predefined limit.

15. The log stream compression system of claim 11, wherein said system is further adapted to remove one or more logically deleted entries located within said compression zone from said log stream.

16. The log stream compression system of claim 11, wherein said system is further adapted to remove said one or more active entries from said one or more first positions.

17. A system of compressing a log stream, said system comprising:

means for locating a logically deleted element on a first queue, said first queue comprising a plurality of elements representative of a plurality of entries of said log stream;

means for dequeuing from said first queue said logically deleted element and one or more active elements of said first queue;

means for enqueuing onto a second queue the dequeued elements; and

means for rewriting one or more entries of one or more first positions of said log stream to one or more second positions of said log stream, said one or more entries corresponding to one or more active elements of said second queue.

18. The log stream compression system of claim 17, further comprising means for removing from said log stream one or more of the enqueued elements.

19. The log stream compression system of claim 17, wherein said one or more first positions is at or near a tail of said log stream and said one or more second positions is at or near a head of said log stream.

20. The log stream compression system of claim 17, wherein at least one of said one or more second positions is on another log stream.

21. A log stream compression system comprising:

a system adapted to determine when a log stream includes a predefined amount of reusable space, said system adapted to determine comprising adapted to check whether a count of logically deleted entries of said log stream has reached a predefined limit; and

said system being further adapted to rewrite, when said log stream includes said predefined amount of reusable space, one or more entries of one or more first positions of said log stream to one or more second positions, said one or more entries being active entries.

22. The log stream compression system of claim 21, wherein said system is further adapted to remove said one or more rewritten entries from said one or more first positions, and to remove one or more logically deleted entries from said log stream.

23. The log stream compression system of claim 21, wherein at least one of said one or more second positions comprises one of the following:

a location at or near a head of said log stream; and

a location within another log stream.