DBCC could not obtain a lock on object 4 because the lock request timeout period was exceeded

Does DBCC CHECKDB perform locks ? No , it doesn’t. What you are seeing here are blocking

Few days ago I got the above error message after performing the weekly consistency checks on one of the client databases. And I was telling myself Paul R has got it wrong, but then there is the two exceptions. J

As you may know from SQL 2005 onwards DBCC CHECK DB does not does not take any locks and then increased concurrency when the running the consistency checks. However, the new approach does considerable reada-heads which bloats the I/O subsystem causing a large drop in workload that’s consistent with blocking. (sqlserverpro, Locking and DBCC CHECKDB, http://www.sqlmag.com/blog/sql-server-questions-answered-28/database-administration/locking-dbcc-checkdb-143608)

The two circumstance where DBCC CHECKDB locks are

- If the TABLOCK option is specified when executing DBCC CheckDB

- The underlying snapshot is not created due to performance reasons or lack of disk space

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