How to switch database mirror roles in SQL Server?
The principal server disconnects clients from the principal database, sends the tail of the log to the mirror server, and, in preparation for switching to the mirror role, sets the mirroring state to SYNCHRONIZING. The mirror server records the log sequence number (LSN) of the last log record received from the principal as the failover LSN.
When does a mirror server take over the database?
In high-safety mode with automatic failover, once the database is synchronized, if the principal database becomes unavailable, an automatic failover occurs. An automatic failover causes the mirror server to take over the role of principal server and bring its copy of the database online as the principal database.
Why does a mirror server need to be synchronized?
The mirror database must already be synchronized. This guarantees that all of the log sent to the mirror server has been written to disk. The principal server has lost communication with the rest of the database mirroring configuration, while the mirror and witness retain quorum.
Can you move data from one mirrored database to another?
As you may know, you cannot detach a mirrored database or bring it offline to move a data or log file from one drive to another drive.
What happens when a database mirror server fails?
If the node running the current principal server fails, automatic failover of the database begins within a few seconds, while the cluster is still failing over to another node. The database mirroring session fails over to the mirror server on the other cluster or unclustered computer, and the former mirror server becomes the principal server.
Where to mirror a database in a cluster?
If you intend to mirror a database in high-performance mode, consider placing the principal server on the failover clustered instance of a cluster and placing the mirror server on an unclustered server in a remote location.