ORA-16642
DB_UNIQUE_NAME mismatch.
Cause
The DB_UNIQUE_NAME value did not match the actual DB_UNIQUE_NAME value for the member that the broker contacted using the connect identifier associated with that member.
Action
Verify that the connect identifier correctly connects to the intended member. Verify that the name of the member the broker expects to find by that connect identifier matches the actual DB_UNIQUE_NAME for that member.