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What are database snapshots in SQL Server?
Database snapshots are like a view of a database as it was at a certain point in time. It is a read-only copy of the data and the state of the pages, which are made possible using a pointer file called the sparse file.
What are the DBCC commands in SQL Server?
Validation Statements
- DBCC CHECKALLOC.
- DBCC CHECKCATALOG.
- DBCC CHECKCONSTRAINTS.
- DBCC CHECKDB.
- DBCC CHECKFILEGROUP.
- DBCC CHECKIDENT.
- DBCC CHECKTABLE.
What is the use of DBCC command?
Microsoft SQL Server Database Console Commands (DBCC) are used for checking database integrity; performing maintenance operations on databases, tables, indexes, and filegroups; and collecting and displaying information during troubleshooting issues.
How are database snapshots used in DBCC checkdb?
DBCC commands use an internal reference of database snapshots to validate the required transactional consistency of the database. When we start DBCC CHECKDB, a hidden database snapshot is created. There is no control, however, over these files, since these are created as alternate streams of the files.
How does checkdb work in SQL Server 2005?
For SQL Server 2005, CHECKDB uses an internal database snapshot to provide the required transactional consistency. So when CHECKDB starts in SQL Server 2005, the first thing it does is work out whether it can run online – if so it creates a hidden database snapshot of the source database (i.e. CHECKDB’s target database).
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.
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.