October 26, 2011 at 10:52 am
Hi all,
I'm new to the SQL server forums - I am an "accidental" DBA that would like to understand more around monitoring SQL server performance (I am a SharePoint administrator).
I read Jonathan Kehayias' post on Page Life Expectancy with great interest and would just like to confirm my high level understanding of it.
Assuming that the classic MS recommendation around PLE (start investigating performance issues if PLE consistently dips below 300 for approximately 4GB of memory) is correct, am I right in thinking that the "minimum" PLE increases linearly with the amount of installed RAM?
e.g. If I have a server with 64 GB of RAM, my "minimum" PLE would be (64/4) * 300 = 4800 seconds, or just over 80 minutes.
I appreciate that there is probably a lot more to this than my question indicates but would like to know if this is a good "rule of thumb" approach for monitoring PLE.
October 26, 2011 at 10:54 am
Well that's pretty much the conclusion they had (in case you didn't read that one) => http://www.sqlskills.com/BLOGS/PAUL/post/Page-Life-Expectancy-isnt-what-you-think.aspx
October 26, 2011 at 11:02 am
Personally my take on PLE is if it drops below what's normal for your system (sustained drop, not a spike), then there's potentially a problem. Jonathan's figure is great for starting when you don't know what is normal, and a good lower limit of what's OK.
p.s. for accidental DBAs, I strongly recommend this: http://www.simple-talk.com/books/sql-books/troubleshooting-sql-server-a-guide-for-the-accidental-dba/ </shameless plug>
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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