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What does the Perfmon counter "Suboptimal plans/sec" actually measure?

Submitted by: @import:stackexchange-dba··
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thewhatsuboptimalsecactuallydoesperfmonmeasurecounterplans

Problem

In SQL Server, what does the Perfmon counter "Workload Group Stats:Suboptimal plans/sec" measure?

It's one of the Resource Governor counters, so it's measured at the workload group (which you have whether you configure RG or not.)

I'm not asking what makes a good plan or a bad plan, but what specifically does that counter measure, and where do you go to find the exact corresponding plans? For example, I can't find anything in Extended Events that would seem to match to a query triggering the "Suboptimal plans/sec" counter.

Solution

There are two items this counter tracks:

  • Timeout



  • Memory Limit Exceeded



The values can be found in the XML plan as Max has proposed in the comments. I can confirm it has been this way since at least SQL Server 2008.

Kudos to @Max Vernon and @Joe Obbish.

The MSDN BOL Technet Docs description isn't super helpful.

Context

StackExchange Database Administrators Q#169120, answer score: 7

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