mirroring state of the database went to disconnected state in SQL Server 2008

I have 4 databases mirrored using High Protection mode without witness server between two servers(principal and mirror) that are in the same domain. Manual failover worked fine for several days. But later somehow the IP of the principal server was changed in the DNS, then onwards the mirror state of these databses went to disconneted state and it remained in that state only though I did ch开发者_开发问答ange the principal servers IP to its original in the DNS server.

Why it remained in disconnected state and how to make the mirror state as synchronized?

The IP is irelevant, unless you set the partner name using IPs (which you shouldn't). The mirror is diconnected betcause the principal cannot connetc to it. You will need to investigate why this is the case:

1. Validate the correctness of partner names on both sides (principal and mirror). Check sys.database_mirroring
2. Verify the errorlog for any connectivity related messages, on both sides
3. use SQL Profiler to monitor for events in the Audit Database Mirroring Login Event Class, Database Mirroring State Change Event Class and Broker:Connection Event Class, on both sides
4. Initiate a manual mirroring session resume: alter database <dbname> set partner resume; on principal