Guru's Guide to SQL Server™ Stored Procedures, XML, and HTML, The

Undocumented Trace Flags

SQL Server trace flags are integer values that you pass to the server to enable special functionality, to provide better diagnostic or system internal info, or to work around problems. You enable trace flags primarily by calling DBCC TRACEON(), but they can also be turned on via the –T server command-line option. Some options only make sense on a serverwide basis, so they're best specified on the server command line. Some only make sense within a particular connection, so they're enabled with DBCC DBCC TRACEON(flagnum), where flagnum is the flag to be set. DBCC TRACEOFF() is the counterpart to TRACEON(). It turns off specific trace flags for a connection. Separate multiple flags with commas to set/unset them at once. ...