MIRRORING BREAKAGE SCENARIOS

In this post i give a summary of what to do when mirrorring breaks down due to some reason. Here lets assume that the Principal is A and the Mirror is B.

Principal Lost

Safety Full With Witness

B is the new Principal now and the mirroring state is DISCONNECTED. When A becomes online, it resumes role as a Mirror automatically (ie we dont have to set up mirroring all over again) except that the session remains suspended until a resume command is issued in B (the new Principal). To do this run the following command in B (the new Principal). 

ALTER DB SET PARTNER RESUME - no re-establishing required

Safety Full Without Witness

On mirror, execute the following

ALTER DB SET PARTNER OFF
RESTORE DB WITH RECOVERY

Then when A becomes online, re-establish mirroring

OR

ALTER DB SET PARTNER FORCE service_allow_data_loss     ###
ALTER DB SET PARTNER RESUME - (no re-establishing required)

Safety Off 

Same as ###

Mirror Lost

ALTER DB SET PARTNER OFF

Then re-establish the mirroring session.