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Spotlight on SAP ASE 2.11 - User Guide

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Pages Read chart

Buffer Pool Pages Read chart*

Use this chart to graphically compare the number of pages read into each pool defined to the selected cache.

Tuning the performance of a data cache's buffer pool configuration can have a dramatic effect on application response times. A poorly configured cache pool can have the reverse effect on an Adaptive Server.

  • A pool that is unused hurts performance. If you add a large I/O (16K) pool, but none of your queries use it, you have taken space away from the small I/O (2K) pool. The 2K pool's cache hit ratio is reduced, and I/O is increased.

  • A pool that is overused hurts performance. If you configure a 16K pool with too little space, and virtually all of your queries use it, I/O rates are increased. The respective 2K cache will be under-utilized, while pages are rapidly cycled through the 16K pool. The cache hit ratio in the 16K pool will be very poor.

  • If you balance your pool utilization within a cache, performance can increase dramatically. Both large I/O (16K) and small I/O (2K) queries experience improved cache hit ratios. The large number of pages often used by queries that perform 16K I/O do not flush 2K pages from disk. Queries using 16K will perform approximately one-eighth the number of I/Os required by 2K I/O.

*Available only in Adaptive Server versions or later


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