BufferPool Statistical Analysis

Statistics for Buffer Pool: BP0

Buffer size is........................4K

Number of VP Buffers is..........10,000

VP sequential threshold is..........80%

Number of HP Buffers is...............0

HP sequential threshold is..........80%

Hiper Space Castout is................Y

Verticle Write Threshold............10%

Horizontal Write Threshold..........50%

Number of GetP................2,379,499

Number of Sequential Access..1,429,246 60.1% of GetP

Number of Random Access........709,940 29.8% of GetP

Number of RID_List.............240,313 10.1% of GetP

Number of Random Misses........277,488 77.1 Misses per Sec

Number of Misses (others)......149,291 41.5 Misses per Sec

Number of No_Reads.................604 0.0% of GetP

Number of Hits...............1,952,116 82.0% of GetP (Appl. HIT RATIO)

System HIT RATIO..................34.7 %

Avg. Page Residency................250 Seconds

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Notes:

Based on the 198 records we obtain these statistics, that show a 69.6 % overall pool ratio. This, however, is the application hit ratio because it doesn’t consider the number of pages read by prefetch functions. While the application hit ratio is the real measure of application I/O delay, the system hit ratio is equally, and sometimes more important, since we are tuning a ‘Global Resource’ - a system buffer pool.

Note the wide difference between the application hit ratio and the system hit ration on the next overhead.

The analysis is continued on the next two slides.