How to troubleshoot Flush Cache error message in SQL Server Logs

25 January,2016 by Jack Vamvas

Question: I’m getting a Flush Cache message in the SQL Server Logs.

FlushCache: cleaned up 3606 bufs with 476 writes in 69033 ms (avoided 4 new dirty bufs) for db 7:0

What does it mean regarding sql server performance? Are there methods I should be using to troubleshoot this message

Answer:  The impact on SQL Server performance will depend on understanding the context . Checkpoint logging causes this message to appear in the SQL Server logs. Just to be specific, these messages only started appearing in the  logs since 2012. Prior to 2012 you needed to turn on a trace flag,

Typically – I’ve found it to be a combination of : a) the sub storage system not maintaining the throughput required  to support the applications and b) higher than usual amounts of data IO.    These are broad guidelines and requires some more detailed analysis. Some suggestions to assist in the troubleshooting process.

  1. Confirm sub storage system is in good shape. Read Storage Checklist FAQ - SQL Server DBA  for some detailed information on how to discuss with your disk administrator
  2. SQL Server health Check
  3. Disk perfmon  . Read  Measuring SAN Performance with Avg Disk Transfer and disk bytes ...
  4. Ask the right questions –SQL Performance tuning - Asking the right question - SQL Server DBA
  5. Look for patterns on spikes in storage demands. Are there any regular intensive jobs which are grinding the storage to a halt? This can get complicated in a shared environment

Author: Jack Vamvas (http://www.sqlserver-dba.com)


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