what is SQL Server Buffer Cache hit ratio? | SQL Server Performance Forums

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what is SQL Server Buffer Cache hit ratio?

how to know the SQL Server Buffer Cache hit ratio? please let me know the query ?

Welcome to the forums.
Are you really referring to the SQL Server 2011 (DENALI) related information here or is it a generic question about Buffer Cache hit ratio?
As per the documentation Buffer-cache hit ratio is:
  • Buffer Cache: This is the pool of memory pages into which data pages are read. An important indicator of the performance of the buffer cache is the Buffer Cache Hit Ratio performance counter. It indicates the percentage of data pages found in the buffer cache as opposed to disk. A value of 95% indicates that pages were found in memory 95% of the time. The other 5% required physical disk access. A consistent value below 90% indicates that more physical memory is needed on the server.
For information :
  • Procedure cache is the area of memory where SQL stores your query plans.
    • Buffer cache is the area of memory where data pages are stored.
  • Relevant perfmon counters:
    • Buffer cache hit ratio
      • Page life expectancy
        • Page reads/sec

how to measure page reads/sec? is page life expe. is in %?
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