How to fix the Oracle error ORA-09987: unable to attach to SGA in READ-ONLY mode?

In this post, you’ll learn more about the Oracle ErrorORA-09987: unable to attach to SGA in READ-ONLY mode with the details on why you receive this error and the possible solution to fix it.

Oracle Error Description

ORA-09987: unable to attach to SGA in READ-ONLY mode

Reason for the Error ORA-09987: unable to attach to SGA in READ-ONLY mode

The instance is not up, or SGA segments are not read-accessible

How to fix the Error ORA-09987: unable to attach to SGA in READ-ONLY mode ?

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

Verify that the instance is up and read permissions for the SGA segments are set.