How to translate output from Wait Stats dmv?

Last Post 21 Feb 2011 07:17 PM by trans53. 2 Replies.
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trans53
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21 Feb 2011 09:25 AM

Hi guys,

By getting this sample result below i am trying to understand how i can translate this output, what to pay attention to and so on.
I often read about "if you see a high value" then do this.... but what is the high value in reality?
Should i pay attention to wait types with "% Signal Waits" > 20% or 30% and not others. Should i pay attention to the numbers for "% Res Waits"?
What are appropriate values for "Avg Wait ms"? Is there a combination of wait types that i need to pay more attention?
These types of questions.

Is there a document where i can learn all about this?

Thanks

I got this result (top 8) below from our main production server.


Wait Type Requests Total Wait Time (ms) Max Wait Time (ms) % Waits Resource Waits (ms) % Res Waits     Signal Waits (ms)  % Signal Waits Avg Wait ms
***Total*** 1081739  2698030   0   100 2565589   100  132441   100  2.49
WRITELOG 281460  826128   150   30.6 808600   31.5  17528   13.2  2.94
IO_COMPLETION 238137  363235   847   13.5 360648   14.1  2587   2  1.53
CXPACKET 30551  348210   59317   12.9 318722   12.4  29488   22.3  11.4
PAGEIOLATCH_SH 41890  305503   897   11.3 305022   11.9  481   0.4  7.29
BACKUPIO 11348  275019   759   10.2 274587   10.7  432   0.3  24.24
PAGEIOLATCH_EX 140513  258248   660   9.6 257835   10  413   0.3  1.84
LATCH_EX 32077  133459   3463   4.9 126572   4.9  6887   5.2  4.16
SOS_SCHEDULER_YIELD 253019 67180   83   2.5 352   0  66828   50.5  0.27

gunneyk
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21 Feb 2011 01:31 PM
I recommend you read the past artilces I have written in SQL Magazine for some of these answers. http://www.sqlmag.com/Authors/Autho...uthor=1745
Another resource is this Technet article and the others it references: http://technet.microsoft.com/en-us/...66540.aspx

But in a nut shell the average wait times I see don't seem to be excessive but most of your waits are I/O related. The signal wiat times will indicate how much of those waits are related to lack of processing time meaning if you are CPU bound or not. Again while yours is not excessive it is worth investigating or watching to see why so much signal waits for certain wait types.
trans53
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21 Feb 2011 07:17 PM
Thank you Andrew!
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