We recently migrated our production server from SQL 2005 (Standard) on Win2003(32-bit) to SQL2012 (Standard; v11.0.3000) on Win2008-R2(64bit). Single-server Dell R510 with 1.2TB storage. Everything went smoothly; the only nagging issue remaining is failure of our maintenance jobs. I tracked the issue down to failure of DBCC CHECKDB. Specifically, the error is:
Executed as user: NT SERVICE\SQLSERVERAGENT. The database could not be exclusively locked to perform the operation. [SQLSTATE 42000] (Error 5030) Check statement aborted. The database could not be checked as a database snapshot could not be created and the database or table could not be locked…
I have Googled this issue and read extensively. For instance, informative blogs (albeit dated) such as these by Paul Randal (Managing Director, SQLskills.com):
www.sqlskills.com/blogs/paul/issues-around-dbcc-checkdb-and-the-use-of-hidden-database-snapshots/
www.sqlskills.com/blogs/paul/checkdb-from-every-angle-complete-description-of-all-checkdb-stages/
As others have noted:
CheckDB by default takes an internal DB snapshot to get the consistent, point-in-time view of the DB that it needs. If that snapshot creation fails, then it will try to get an exclusive database lock before proceeding (same as if you had executed DBCC CHECKDB WITH TABLOCK). The root problem is not that the lock could not be obtained, it's that the internal database snapshot could not be created.
msdn.microsoft.com/en-us/library/ms188796.aspx details the specific situations when an internal database snapshot is not created and table locking is attempted. None of these situations apply. Which only leaves me with the permissions issue discussed in Paul Randal’s blog referenced above. I have verified the SQLSERVERAGENT service account has full permissions on the SQLDATA directory where the databases reside and has full permissions on each database within the directory. Just for giggles, I created a job (run as SQLSERVERAGENT) that creates and then deletes a text file in the SQLDATA directory. It runs fine.
Also tested… I get the snapshot creation error when manually running DBCC CHECKDB against any of our databases and when executing under a variety of administrator accounts that are members of the SQL sysadmin role and the Domain Admins security group (the Domain Admins is a member of the local Administrators group that has full permissions on all SQL directories/folders).
Additionally, the databases in question are small (200MB to 6GB) and the disk has plenty of elbow room (978GB free on 1.22TB RAID5 array) to create the internal database snapshots.
So, I am stumped… CHECKDB doesn't surface an error message that is detailed enough to determine the precise cause of the error. I would really like to hear from someone who is successfully running DBCC CHECKDB on the SQL2012 (Standard) on a Win2008 R2 (64-bit) server.
Thanks!