You can check the status of mirroring, endpoints, certificates, and users with the following query:
select * from sys.database_mirroring
select * from sys.database_mirroring_endpoints
select * from sys.tcp_endpoints
select * from sys.certificates
select * from sys.database_principals
You can also check the state of the database mirroring by performing the following steps:
Open SQL Server Management Studio.
Connect to the principal server.
Right click on the mirrored database to display menu options.
Choose the Tasks > Launch Database Mirroring Monitor menu option. The Database Mirroring Monitor appears, showing the status of the database that is being monitored.