Buffer cache hit ratio negative

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Article ID: 140356

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Updated On:

Products

DX Infrastructure Management NIMSOFT PROBES

Issue/Introduction

We have UIM 9.0.2 with oracle agent 5.41 monitoring one oracle RAC version  11.2.0.4.
We enabled the buf_cachehit_ratio checkpoint but sometimes it returns s negative value that should not be correct:

 

Profile PORTAL, instance portal2, buffer cache hit-ratio (-40.63%) is too low
 
 
 
 
 
 

Cause

This is caused by getting a bad value from Oracle.

Environment

Release : 9.0.2

Component : UIM - ORACLE

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

Resolution

Please consult with your Oracle DBA to see if the result set of this query ever returns a negative number:



SELECT a.value as db_block_gets,

     b.value as consistent_gets,

     c.value as physical_reads,

     d.value as pr_direct,

     e.value as pr_direct_lob,

     f.value as pr_direct_temp_space

 FROM v$sysstat a, v$sysstat b, v$sysstat c, v$sysstat d, v$sysstat e, v$sysstat f

WHERE a.name = 'db block gets' AND b.name = 'consistent gets' AND c.name = 'physical reads' AND d.name = 'physical reads direct'

 AND e.name = 'physical reads direct (lob)' AND f.name = 'physical reads direct temporary tablespace';