Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-03-04
2001-08-14
Homere, Jean R. (Department: 2177)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06275826
ABSTRACT:
TECHNICAL FIELD
This invention relates, in general, to the management of log streams of a multisystem environment and, in particular, to pacing the frequency at which the log streams are compressed by systems of the multisystem environment.
CROSS REFERENCE TO RELATED APPLICATIONS
This application contains subject matter which is related to the subject matter of the following applications, each of which is assigned to the same assignee as this application, and each of which is hereby incorporated herein by reference in its entirety:
“Method Of Pacing The Frequency At Which Systems Of A Multisystem Environment Compress Log Streams,” by Geiner et al., Ser. No. 09/262,250, filed herewith;
“Pacing The Frequency At Which Systems Of A Multisystem Environment Compress Log Streams,” by Geiner et al., Ser. No. 09/262,587, filed herewith;
“Tail Compression Of A Sparse Log Stream Of A Computer System,” by Clark et al., U.S. Pat. No. 5,920,875, filed on Mar. 28, 1997;
“Tail Compression Of A Log Stream Using A Scratch Pad Of Logically Deleted Entries,” by Clark et al., U.S. Pat. No. 5,966,708, filed on Mar. 28, 1997;
“System Of Compressing A Log Stream Using A Scratch Pad Of Logically Deleted Entries,” by Clark et al., U.S. Pat. No. 6,108,667, filed on Mar. 28, 1997;
“A Method of One System Of A Multisystem Environment Taking Over Log Entries Owned By Another System,” by Clark et al., U.S. Pat. No. ,076,095, filed on Mar. 28, 1997;
“One System Of A Multisystem Environment Taking Over Log Entries Owned By Another System,” by Clark et al., U.S. Pat. No. 6,092,084, filed on Mar. 28, 1997;
“System Of Compressing The Tail Of a Sparse Log Stream Of A Multisystem Environment,” by Clark et al., U.S. Pat. No. 6,125,393, filed on Mar. 28, 1997;
“System Of Compressing The Tail Of A Sparse Log Stream Of A Computer System,” by Clark et al., U.S. Pat. No. 5,956,735, filed on Mar. 28, 1997;
“Tail Compression Of A Sparse Log Stream Of A Multisystem Environment,” by Clark et al., U.S. Pat. No. 5,999,935, filed on Mar. 28, 1997; and
“Method And System For Log Management In A Coupled Data Processing System,” by Geiner et al., U.S. Pat. No. 5,737,600, issued on Apr. 7, 1998.
BACKGROUND ART
In various computer systems, historical log data is maintained in, for instance, log files for use in system recovery, problem determination and/or system maintenance. Typically, these log files have a limited amount of capacity to retain the historical data. After the capacity is met, at least some of the data records are moved from the log files to external storage devices, such as direct access storage devices (DASD), thereby providing additional space in the log files for more data.
At some point, data within the log files and/or on the external storage devices is no longer needed. For example, there is no need to keep the data once it passes its retention requirements. The saving of data past its usefulness adversely affects system performance in a number of ways. For instance, when unnecessary data is retained and a log file needs to be browsed to recover logged data during recovery of a failure, the browser may have to deal with potentially large amounts of unnecessary data, thereby slowing down the recovery process. Additionally, when the saving of unwanted data records requires the use of external storage devices, which typically provide slower access to the data, the reading of the data takes longer, thus, affecting system performance.
Therefore, it is beneficial to delete any unnecessary data from the log files. This is accomplished by compressing the log files and then physically deleting any entries that can be deleted. When a log file is used by various systems of a multisystem environment, each of the systems is responsible for compressing and deleting its unwanted entries.
When the systems of the multisystem environment are processing at different transaction rates, however, and the slower system does not adequately compress the log file at a rate commensurate with the faster system, the slower system adversely affects the performance of the faster system. This is true regardless of whether the reason for the disparity in transaction rates is hardware performance characteristics or work load differences. Thus, the faster system potentially has many more elements in the log file than the slower system, and the elements of the faster system can be separated by a single element written by the slower system. This problem may be exacerbated when there are several fast systems and only one slow system.
Based on the foregoing, a need exists for a capability that provides for the pacing of the frequency at which a system compresses a multisystem log file. A further need exists for a capability that allows each system to adjust its compression rate based on the compression rates of the other systems, thus ensuring a minimal sized log file. A further need exists for a pacing technique that allows the frequency of compression to be adjusted in real-time based on the current transaction rates of the systems connected to the log file.
SUMMARY OF THE INVENTION
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of an article of manufacture including at least one computer usable medium having computer readable program code means embodied therein for causing the pacing of the frequency at which multisystem log streams are compressed. The computer readable program code means in the article of manufacture includes, for instance, computer readable program code means for causing a computer to ascertain a rate at which a multisystem log stream is compressed by one system of a multisystem environment. The rate is relative to how frequently the multisystem log stream is compressed by at least one other system of the multisystem environment. The article of manufacture further includes computer readable program code means for causing a computer to adjust, in real-time, the frequency at which the one system compresses the multisystem log stream.
In one example, the computer readable program code means for causing a computer to ascertain includes computer readable program means for causing a computer to check a compress lag count of the one system. In a further example, the article of manufacture includes computer readable program code means for causing a computer to update the compress lag count when the one system compresses the multisystem log stream.
In another embodiment of the invention, the computer readable program code means for causing a computer to adjust includes computer readable program code means for causing a computer to increase the frequency at which the one system compresses the multisystem log stream, when the ascertained rate indicates that the one system is compressing the multisystem log stream at a slower rate than at least one other system.
In another embodiment of the invention, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform a method of pacing the frequency at which multisystem log streams are compressed, is provided. The method includes, for instance, ascertaining a rate at which a multisystem log stream is compressed by one system of a multisystem environment; comparing, at predefined time intervals, the ascertained rate to a predefined value to determine whether the frequency at which the one system compresses the multisystem log stream is to be adjusted; adjusting, in real-time, the frequency at which one system compresses the multisystem log stream, when the comparing indicates adjusting; determining whether the time of the predefined time intervals is to be modified; and modifying the time of the predefined time intervals to adjust how often the comparing is performed, when it is determined that the time is to be modified.
The compression pacing capability of the present invention advantageously adjusts, in real-time, the frequency at which systems compress a multisystem log stream. Each system adjusts its compression rate based on the compressi
Geiner Robert Vaughn
Greenspan Steven Jay
Kinder Stephen Joseph
Zobre Douglas Michael
Esq. Lily Neff
Heslin & Rothenberg, P.C.
Homere Jean R.
International Business Machines - Corporation
Robinson Greta L.
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