Oracle Error ORA-12523: TNS:listener could not find instance appropriate for the client connection

Oracle Error Message

ORA-12523: TNS:listener could not find instance appropriate for the client connection

Reason for the Error

The listener could not find any available (database) instances, that are appropriate for the client connection.

Solution

Run “lsnrctl services” to ensure that the instance(s) are registered with the listener, and have status READY.