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SQL Database Mirroring and SQL Logins




After-failing over a databases to the mirror instance, the application couldn’t login to the databases complaining of login issues.
It was later identified that the SQL logins were not created when the mirroring sessions were created. So I took the responsibility of creating the logins but didn’t realize the importance of the SID impact on the mirror instance and executed SP_Change_user_login to map the login with the respective database users.

After the failover testing was completed on the mirror instance the databases were failed back over to the primary instance at which point we ran into further login issue. Even though the problem was sorted by executing SP_Change_user_login I obviously hadn’t ironed out the problem.

After backtracking my steps I realized the importance of creating the SQL login with the same SID  in mirror instance to the same of the primary instance. Following is the syntax for the creation of the loginwith hased SID

CREATE LOGIN MirrorDB WITH password =
0x0100F2C6ADC64E59D28531B1000DCADB0F881E51D9329F358A0B
 hashed, sid =
0x3C1025E1DBC23D469CF1E9141258A0EB
, default_database =Master, CHECK_EXPIRATION=OFF, CHECK_POLICY=OFF


Even though the SID is easily retrievable from Syslogins the password is not in binary format which doesn’t really help. And the easiest way of getting this sorted is to use the sp_help_RevLogin which is available at http://support.microsoft.com/kb/918992.

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