Fix the principal

--On the principal

--create a new cert for the endpoint

USE master;

CREATE CERTIFICATE [principal_new_cert]

WITH SUBJECT = 'mirroring cert',

START_DATE='07/11/2010', --make sure this is a day prior to the current date

EXPIRY_DATE='07/12/2020'; --make sure this is set out 10-20 years

GO

--backup the cert for the endpoint

BACKUP CERTIFICATE [principal_new_cert] TO FILE = 'c:\principal_new_cert.cer';

GO

--set mirroring to use the new cert

ALTER ENDPOINT DBMirrorEndPoint FOR DATABASE_MIRRORING (AUTHENTICATION = CERTIFICATE [principal_new_cert])

GO

--finally delete the old cert for the endpoint

DROP CERTIFICATE [old_principal_cert]

GO

Fix the mirror

--On the mirror

--drop the old cert for the principal login

DROP CERTIFICATE [old_principal_cert]

GO

--create the new cert using the backup you made on the principal server

CREATE CERTIFICATE [principal_new_cert] AUTHORIZATION PrincipalServerUser

FROM FILE = 'c:\principal_new_cert.cer'

GO

--create a new cert for the endpoint

USE master;

CREATE CERTIFICATE [mirror_new_cert]

WITH SUBJECT = 'mirroring cert',

START_DATE='07/11/2010', --make sure this is a day prior to the current date

EXPIRY_DATE='07/12/2020'; --make sure this is set out 10-20 years

GO

--backup the new cert for the endpoint

BACKUP CERTIFICATE [mirror_new_cert] TO FILE = 'c:\mirror_new_cert.cer';

GO

--set mirroring to use the new cert

ALTER ENDPOINT DBMirrorEndPoint FOR DATABASE_MIRRORING (AUTHENTICATION = CERTIFICATE [mirror_new_cert])

GO

--finally delete the old cert for the endpoint

DROP CERTIFICATE [old_mirror_cert]

Finish the principal

--Go back to the principal

--drop the old cert for the mirror login

DROP CERTIFICATE [old_mirror_cert]

GO

--create the new cert using the backup you made on the mirror server

CREATE CERTIFICATE [mirror_new_cert] AUTHORIZATION MirrorServerUser

FROM FILE = 'c:\mirror_new_cert.cer'

GO

--finally resume the mirroring session for each database

ALTER DATABASE [mirrored_database_name] SET PARTNER RESUME