Making Sense of Performance Statistics

Making Sense of Performance Statistics

Post by michael brul » Tue, 13 Oct 1998 04:00:00

I'm having a little trouble making sense of some statistics I get from
my servers.  We run DBCC SQLPERF weekly, just before shutting down and
re-booting the servers, so the  information below covers a seven day
period.  I'm looking specifically at LRUStats:

         Statistic                        Value                
 -------------------------------- --------------------
 Cache Hit Ratio                             99.401001
 Cache Flushes                           619846.000000
 Free Page Scan (Avg)                       100.802818
 Free Page Scan (Max)                         1.000000
 Min Free Buffers                          5529.000000
 Cache Size                               94350.000000
 Free Buffers                              5660.000000

Microsoft recommends that Cache Flushes not exceed 100 and Free Page
Scan Avg. not exceed 10.  My confusion stems from the fact that we
regularly and significantly exceed the recommended maximum without any
noticeable degradation of performance.  Could someone shed some light on
why this is so or point me toward a more meaningful interpretation of
these numbers?