High Page life expectancy

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High Page life expectancy

Loner

SSC-Insane

Points: 21279
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October 26, 2011 at 8:01 am

#250057

I ran this query:
SELECT [object_name],
[counter_name],
[cntr_value]
FROM sys.dm_os_performance_counters
WHERE [object_name] LIKE '%Manager%'
AND [counter_name] = 'Page life expectancy'
The result I got is 55881.
Is it meant I need more memory?
I am running SQL Server 2008 R2 standard version and the database size is 883527.00 MB.
Thanks

Viewing 7 posts - 1 through 6 (of 6 total)

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adb2303 SSCertifiable Points: 7588 More actions · Answer 1

55881 seems pretty healthy to me. Are you seeing other symptoms of memory pressure?

Andrew

dajonx SSCertifiable Points: 6950 More actions · Answer 2

Keep this in mind:

http://www.sqlskills.com/BLOGS/PAUL/post/Page-Life-Expectancy-isnt-what-you-think.aspx

My Blog!

Loner SSC-Insane Points: 21279 More actions · Answer 3

I thought it supposed to be 300.

What number is good and what number is bad?

I don't understand the number meant. Can you explain?

Thanks

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 4

Loner (10/26/2011)
I thought it supposed to be 300.

10 years ago if page life expectancy dropped below 300 it was considered bad. Many people still blindly quote 300 as the figure it shouldn't go under without understanding what that figure means

What number is good and what number is bad?
I don't understand the number meant. Can you explain?

Did you read the blog post?

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

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Jack Corbett SSC Guru Points: 184394 More actions · Answer 5

Loner (10/26/2011)
I thought it supposed to be 300.
What number is good and what number is bad?
I don't understand the number meant. Can you explain?
Thanks

If you haven't read the blog post, I'll give a quick explanation and Gail can correct me when I'm wrong :-P.

Page Life Expectancy is how long a data page stays in memory. There are no absolutes as to what is a good number as the blog post explains. Essentially the higher the number the better because it usually means you have plenty of memory and you aren't going out to disk as often. You need to establish a baseline for your environment and when it gets below what has been normal you need to investigate why it is falling.

Jack Corbett
Consultant - Straight Path Solutions
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Steve Jones - SSC Editor SSC Guru Points: 736297 More actions · Answer 6

Also this: http://www.sqlskills.com/blogs/jonathan/post/Finding-what-queries-in-the-plan-cache-use-a-specific-index.aspx

Perhaps a better formula for PLE from Jonathan Kehayias.