InstantForum.NET v2.9.0SQLServerCentralhttp://www.sqlservercentral.com/Forums/notifications@sqlservercentral.comWed, 22 May 2013 16:57:19 GMT20http://www.sqlservercentral.com/Forums/Topic1384046-146-1.aspxI can't change server level settings like that without a lot of meetings etc. I'm experimenting on a test system with doing the first big select statement into a temp table using option(maxdop 1 ), then union that to the last select also using the maxdop option. If this works I can create a stored procedure which the application should be able to call with the numerous parameters used in the where clause.MaxClockSpeed: 2128 NumberOfCores: 8 NumberOfLogicalProcessors: 16 Wed, 14 Nov 2012 06:05:17 GMTIndianrockhttp://www.sqlservercentral.com/Forums/Topic1384046-146-1.aspxHow many cpu's?Ok, here is a blind guess that probably isn't optimal for you but is maybe, just might be, could happen to be more optimal than the default.Set maxdop to 4Cost threshhold for parallelism to 35.Test and see if problem goes away. Tue, 13 Nov 2012 22:54:06 GMTSpringTownDBAhttp://www.sqlservercentral.com/Forums/Topic1384046-146-1.aspxMost of our queries are generated by an ORM (object relational mapper). Three weeks ago we put two new sql cluster boxes into service with 512GB of memory. Yesterday a report-type query with a ton of joins and a union was run from the application and it created stack dumps showing error " too many parallel nested transactions." Without more coding, the developers say they can't use a max degree of parallelism option. The server is set at maxdop zero.Sql 2005 Enterprise SP4 9.0.5000 64bitSQL Server Assertion: File: <lckmgr.cpp>, line = 385 Failed Assertion = '0' Too many parallel nested transactions. This error may be timing-related. If the error persists after rerunning the statement, use DBCC CHECKDB to check the database for structural integrity, or restart the server to ensure in-memory data structures are not corrupted.Tue, 13 Nov 2012 05:47:43 GMTIndianrock