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Buffer Cache hit ratio


Buffer Cache hit ratio

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MattF
MattF
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Hi,

We are checking the Buffer cache hit ratio (as % using Buffer cache hit ratio / Buffer cache hit ratio base) sampling every 15 sec. This is nearly always 100% but there are occasional (1 in 10) values which give results way off the normal. The counter and base values have spikes resulting in percentages (eg 5% or 150%) which throw off our trend reporting. We would like to know what the actual base and raw counter values represent (eg. a count of the number of requests for pages in the buffer pool?) and why the base would intermittently differ so erratically from the raw count?
Thanks
Matthew
GilaMonster
GilaMonster
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Rather ignore that counter. It's useless. Even on a server that's under severe memory pressure it'll be sitting near 100%

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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i_amhers
i_amhers
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Hello,

Gila already hit the direction you should take: useless metric and not what you are looking for.

To better explain the reasons why that metric isn't getting you what you think it is please review this awesome post: https://www.simple-talk.com/sql/database-administration/great-sql-server-debates-buffer-cache-hit-ratio/

I spent some time a few weeks ago on this very same task to look up this setting as well. Utilizing information on this post I was able to see actual Buffer Cache Hit Ratio values.

Hope that helps and good luck!

Regards,
Jeremy
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