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 What Are High Wait Times?

Author  Topic 

viperbyte
Posting Yak Master

132 Posts

Posted - 2012-12-10 : 11:24:05
I don't know what are normal, low, acceptable or unacceptable wait times. I see 30000 for WAITFOR, and 118500 for FT_IFTS_SCHEDULER_IDLE_WAIT. These are the highest values and the rest are less but I don't know what is high or not. What is a high?

sunitabeck
Master Smack Fu Yak Hacker

5155 Posts

Posted - 2012-12-10 : 12:58:50
More likely than not, you can ignore both of those wait types. The WAITFOR wait type is a result of WAITFOR statements in your code/queries - which presumably are there by design. I don't have any direct experience with the FT_IFTS_SCHEDULER_IDLE_WAIT wait type, but from reading about it, it looks like that is a wait type that is indicating full text searches idling - waiting for something to do. So unlesss you experiencing any issues with full text searches, you can ignore that as well.

As to how to interepret the wait times, the times are cumulative since the server was restarted last time. If you want to isolate performance for specific periods of time you would need to take the delta after capturing before and after snapshots.
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viperbyte
Posting Yak Master

132 Posts

Posted - 2012-12-10 : 14:37:06
You mean run DBCC SQLPERF('sys.dm_os_wait_stats', CLEAR); then look at the wait time for a particular wait type, monitor it for sometime then DBCC SQLPERF('sys.dm_os_wait_stats', CLEAR); again and do the same monitoring for the same amount of time again? Is that what you mean by taking a delta?
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sunitabeck
Master Smack Fu Yak Hacker

5155 Posts

Posted - 2012-12-10 : 14:41:49
I was thinking about sys.dm_os_wait_stats, along the lines of what is described in this article.

Search for "The important thing to remember is that the metrics for the columns returned when querying sys.dm_os_wait_stats is cumulative" on that page. Starting at around there, he describes taking snapshots and computing the delta.
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viperbyte
Posting Yak Master

132 Posts

Posted - 2012-12-10 : 15:23:05
Thanks sunitabeck. I just speed read the whole article. The begining of it had the best explanation of what the different columns mean in sys.dm_os_wait_stats that I have seen yet. Now I truly understand those columns. And I will definitly give that suggestion a try. Super thanks for the direction :)
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