ORA-01102 cannot mount database in EXCLUSIVE mode

Users might receive error “ORA-01102” when trying to startup

01102, 00000, "cannot mount database in EXCLUSIVE mode"
// *Cause: Some other instance has the database mounted exclusive or shared.
// *Action: Shutdown other instance or mount in a compatible mode.

You will receive this error when instance is already opening in parallel. You can resolve this issue by shutting down all the instances before mounting the database.

Verify that no background processes running owner as oracle
Ps –ef |grep <$ORACLE_SID>

If you found any processes then shutdown the instance, if you are not able to shutdown then you can kill by using “kill -9 <processed>.

Now you should be able to startup without any issues.

Regards
Satishbabu Gunukula, Oracle ACE

http://www.oracleracexpert.com