Error message when you use the sys.dm_exec_query_plan dynamic management function to return a Showplan in XML format for a Transact-SQL batch: "A system assertion check has failed" (915050)

SYMPTOMS

Consider the follow scenario. You use the sys.dm_exec_query_plan dynamic management function to return a Showplan in XML format for a Transact-SQL batch. The query execution plan of the Transact-SQL batch resides in the plan cache. When the size of the Showplan exceeds 1 MB in Microsoft SQL Server 2005 32-bit versions or exceeds 0.5 MB in SQL Server 2005 64-bit versions, the query stops. In this scenario, you receive a SQL Server assertion error message in the error log that is similar to the following:

Error: 17066, Severity: 16, State: 1.
SQL Server Assertion: File: <tmpilb.cpp>, line=3131 Failed Assertion = 'fNoWriters'. 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.
Error: 3624, Severity: 20, State: 1.
A system assertion check has failed. Check the SQL Server error log for details

RESOLUTION

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2005. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

913089 How to obtain the latest service pack for SQL Server 2005

WORKAROUND

To work around this problem, run the SET SHOWPLAN_XML ON Transact-SQL statement, and then run the Transact-SQL batch. After you obtain the Showplan for the Transact-SQL batch, run the SET SHOWPLAN_XML OFF Transact-SQL statement. To do this, follow these steps:

In SQL Server Management Studio, connect to the instance of SQL Server 2005.
Click New Query to open a new query editor.
Run the following code.
```
SET SHOWPLAN_XML ON
My_Transact-SQL_batch
SET SHOWPLAN_XML OFF
```
Note My_Transact-SQL_batch is a placeholder for the Transact-SQL batch whose Showplan you want to obtain.

Note You have to run the SET SHOWPLAN_XML ON Transact-SQL statement and the SET SHOWPLAN_XML OFF Transact-SQL statement separately from the rest of the code.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Microsoft SQL Server 2005 Service Pack 1.

REFERENCES

For more information about the SET SHOWPLAN_XML Transact-SQL statement, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn2.microsoft.com/en-us/library/ms187757.aspx

For more information about the sys.dm_exec_query_plan dynamic management function, visit the following MSDN Web site:

http://msdn2.microsoft.com/en-us/library/ms189747.aspx