In the SQL Server Database RESTORE there is an option to restore with either a RECOVERY or NORECOVERY option. Understanding the difference and knowing when to apply the options is useful.

When the RECOVERY option is used   such as :

RESTORE DATABASE MyDB WITH RECOVERY;

The RECOVERY command requests the current RESTORE to roll back all uncommitted transactions.  When all uncommitted transactions are rolled back the database is placed into a ready state. The database is ready to use.

A criteria of  database recovery is to ensure all data sets  restored are consistent with the database. Errors are reported if the roll forward data set is not database consistent.

When the NORECOVERY option is used such as:

RESTORE DATABASE MyDB WITH NORECOVERY;

The NORECOVERY command requests that no uncommitted transactions are rolled back.  As a result, roll forward can continue with the next statement in the RESTORE sequence.  

 Typically the NORECOVERY is used in situations :

 a)       A further transaction log file has to be applied. For example,  a failure may occur and a RESTORE is required form the last known good LOG BACKUP. The situation may require:

--–  Restore last full backup but don’t recover
RESTORE DATABASE myDB    WITH NORECOVERY;
--- Restore Logs , repeat as often as required
RESTORE LOG myDBLog  WITH NORECOVERY;
           ---Database recovery 
RESTORE DATABASE MyDB WITH RECOVERY;

 b)  A DIFFERENTIAL file has to be applied

 --–  Restore last full backup but don’t recover
RESTORE DATABASE myDB    WITH NORECOVERY;
--- Restore differential
 RESTORE DATABASE myDBLog  WITH NORECOVERY;
           ---Database recovery 
RESTORE DATABASE MyDB WITH RECOVERY;

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