Database Mirroring Witness Catalog Views (Transact-SQL)
Applies To: SQL Server 2014, SQL Server 2016 Preview
In a database mirroring session, automatic failover requires a witness server. Ideally, the witness resides on a separate computer from both the principal and mirror servers. The witness does not serve the database. Instead, it monitors the status of the principal and mirror servers. If the principal server fails, the witness may initiate automatic failover to the witness server. For more information, see Database Mirroring Witness.
For information about the catalog view for database mirroring witnesses, see sys.database_mirroring_witnesses (Transact-SQL).
For the information about the catalog-view columns for mirrored databases, see sys.databases (Transact-SQL).