Brother-Eagle™ Oracle Performance
Advice: Library Cache Hit Ratio

The library cache hit ratio provides a general indication of how well the library cache is sized for your database. Procedural objects exist in the library cache and when requested, Oracle first looks in the cache. If not in the cache, this is referred to as a "cache miss" and then Oracle must then load it into the cache. The library cache resides in the shared pool within the SGA, so increasing the size of the shared pool can increase the library cache hit ratio. Since nothing is in the cache at start-up, the database should reach a steady state after a period of normal activity.

This parameter is collected at each interval. Therefore, if you specified a 60 second refresh rate, the value displayed applies to the last 60 seconds.

Hit ratios should be used sparingly and should not be the main performance metric reviewed. Ratios should simply be used as performance indicators which may warrant further investigation into other areas.

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