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cache hit ratio and buffer cache hit ratio

  • December 10, 2003 at 1:19 pm

    #107547

    Hi there, I kind of confused with these two ratioes --"cache hit ratio" and "buffer cache hit ratio". I used the Performance Monitor to log the performance of my sql instance, I added these counters in the categories about sqlserver, from the buffer manager/buffer cache hit ratio, and cache manager/cache hit ratio.

    then the cache hit ration I got is around 60, the other one, however, most time is above 98. I know the system looks okay. But I still wonder what's really the difference between these two ratioes, and what's the cache and buffer pool about? data cache? or batch queries?

    I check the explanation for the counters, seems doesn't help to me.

    Thanks!

  • December 10, 2003 at 3:07 pm

    #485617

    The SQLServer:Cache Manager counters, including Cache Hit Ratio are for cached objects, not data pages. The SQLServer:Buffer Manager|Buffer cache hit ratio counter is for cached data pages, as are most of the counters in that category. You should expect the SQLServer:Cache Manager|Cache Hit Ratio number to be lower than that for data pages, as query plans and other objects age out of memory or are automatically recompiled for performance reasons.

    --Jonathan



    --Jonathan

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