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What happens during DBCC Checkdb?
DBCC CHECKDB, from Microsoft MSDN Library, checks logical and physical integrity of all the objects in the specified database by performing the following operations: Runs DBCC CHECKCATALOG on the database – Checks for catalog consistency within the database. Validates the contents of every indexed view in the database.
What does DBCC Checkdb do in SQL Server?
Basically, DBCC CheckDB checks the logical and physical integrity of all objects in the database. This is what DBCC CheckDB does under the hood according to the official Microsoft documentation: Runs DBCC CHECKALLOC on the database – the consistency of disk space allocations.
Can we run DBCC Checkdb on master?
DBCC CHECKDB fails when run against master if an internal database snapshot cannot be created. Running DBCC CHECKDB against tempdb does not perform any allocation or catalog checks and must acquire shared table locks to perform table checks.
Does DBCC Checkdb lock database?
DBCC CHECKDB Overview It does not acquire table locks by default. Instead, it acquires schema locks that prevent metadata changes, but allow data changes.
What happens if DBCC checkdb is not backed up?
If the database is inconsistent or there are storage or allocation problems, the backup will store these too. As such, the results of any possible corruption should surface on the restore. This will completely eliminate the IO issue on the production server.
What causes DBCC checkdb to run faster than SQL Server?
Causes DBCC CHECKDB to obtain locks instead of using an internal database snapshot. This includes a short-term exclusive (X) lock on the database. TABLOCK will cause DBCC CHECKDB to run faster on a database under heavy load, but decreases the concurrency available on the database while DBCC CHECKDB is running.
What does DBCC checkalloc do in SQL Server?
Runs DBCC CHECKALLOC on the database – Checks consistency of disk space allocation structures for a specified database. Runs DBCC CHECKTABLE on every table and view in the database – Checks the integrity of all the pages and structures that make up the table or indexed view.
How does DBCC checkdb work with database mirroring?
DBCC CHECKDB and Database Mirroring. If you have database mirroring setup, you can create a database snapshot explicitly from the mirror and run DBCC CHECKDB on that version of the database. Be aware that the IO load from this could make the REDO queue on the mirror larger and cause the failover to take longer.