MAXDOP-Related Extended Events

Paul Randal looks at a couple of Extended Events which help you find CXPACKET waits and degrees of parallelism:

Now I’ll set up a simple Extended Events session to track down the offending code (based on the query from here). It’s very important that you query the sys.dm_xe_map_values DMV to find the correct number to use in the query for the CXPACKET wait, as these numbers often change from release to release, and even in Service Packs. For instance, CXPACKET was 191 in SQL Server 2014 RTM, but is 190 in the 2014 build I’m using.

Be very careful about running this in production, as the event will fire for *every* wait that occurs and so will likely affect your workload throughput, even though it’ll short-circuit if the wait isn’t CXPACKET. I’ll show you a better event to use lower down.

These are good events to know.

Related Posts

Extended Events Files on Linux

Jason Brimhall looks at an error when trying to set up an Extended Events session on Linux: This will fail before the query really even gets out of the gate. Why? The proc xp_create_subdir cannot create the directory because it requires elevated permissions. The fix for that is easy enough – grant permissions to write to […]

Read More

Auditing Databases in Use

Jason Brimhall shows how you can use Extended Events to figure out if that database is still in use: Here we can see there are indeed some databases that are still in use on this server. If we are looking to retire the instance, or migrate relevant databases to a new server, we have better […]

Read More

Categories

February 2017
MTWTFSS
« Jan Mar »
 12345
6789101112
13141516171819
20212223242526
2728