How to fix the Oracle error ORA-27100: shared memory realm already exists?

In this post, you’ll learn more about the Oracle ErrorORA-27100: shared memory realm already exists with the details on why you receive this error and the possible solution to fix it.

Oracle Error Description

ORA-27100: shared memory realm already exists

Reason for the Error ORA-27100: shared memory realm already exists

Tried to start duplicate instances, or tried to restart an instance that had not been properly shutdown

How to fix the Error ORA-27100: shared memory realm already exists ?

You can fix this error in Oracle by following the below steps

Use a different instance name, or cleanup the failed instance’s SGA