Thursday, May 28, 2015

Investigating a (suddenly) slow running query...

Some Questions / lines of enquiry ...

What else was going on on the server at that time?

  • Is blocking occuring?
  • Is another process monopolising resources (memory, cpu, i/o)

What has changed?

  •  Any code changes
  •  Any configuration change
  •  Any change in data volume (influx of new data)

Is all maintenance happening? (it won't take long to check)

  • Are statistics up to date
  • How is index fragmentation
  • Are backups occurring (remember full backups control log fie growth)
Can the query be run manually?
- Look at Execution plan

Is it a stored procedure?
- Look at Execution plan for parameter differences (parameter sniffing)

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