TNS-12531: TNS:cannot allocate memory
Cause: Sufficient memory could not be allocated to perform the desired activity.
Action: Either free some resource for TNS, or add more memory to the machine. For further details, turn on tracing and re-execute the operation.
TNS-12524: TNS:listener could not resolve HANDLER_NAME given in connect descriptor
Cause: The HANDLER_NAME in the CONNECT_DATA was not found in the listener's tables for the specified SERVICE_NAME and INSTANCE_NAME.
Action: Check to make sure that the specified HANDLER_NAME is correct.
TNS-12523: TNS:listener could not find instance appropriate for the client connection
Cause: The listener could not find any available (database) instances, that are appropriate for the client connection.
Action: Run "lsnrctl services" to ensure that the instance(s) are registered with the listener, and have READY status.
TNS-12522: TNS:listener could not find available instance with given INSTANCE_ROLE
Cause: There are not any available and appropriate database instances registered with the listener, that are part of the service identified by SERVICE_NAME given in the connect descriptor and that have the specified INSTANCE_ROLE (and INSTANCE_NAME, if specified).
Action: Check to make sure that the specified INSTANCE_ROLE is correct. Run "lsnrctl services" to ensure that the instance(s) have registered with the listener and that they are ready to accept connections.
TNS-12521: TNS:listener could not resolve INSTANCE_NAME given in connect descriptor
Cause: The INSTANCE_NAME in the CONNECT_DATA was not found in the listener's tables for the specified SERVICE_NAME.
Action: Check to make sure that the specified INSTANCE_NAME is correct.
TNS-12520: TNS:listener could not find available handler for requested type of server
Cause: None of the known and available service handlers for requested type of server (dedicated or shared) are appropriate for the client connection.
Action: Run "lsnrctl services" to ensure that the instance(s) have registered with the listener and that the appropriate handlers are accepting connections.
TNS-12519: TNS:no appropriate service handler found
Cause: The listener could not find any available service handlers that are appropriate for the client connection.
Action: Run "lsnrctl services" to ensure that the instance(s) have registered with the listener, and are accepting connections.
TNS-12518: TNS:listener could not hand off client connection
Cause: The process of handing off a client connection to another process failed.
Action: Turn on listener tracing and re-execute the operation. Verify that the listener and database instance are properly configured for direct handoff. If the problem persists, contact Oracle Support Services.
TNS-12517: TNS:listener could not find service handler supporting direct handoff
Cause: None of the known service handlers are registered as supporting direct handoff as required for this client connection.
Action: Check that the instance(s) are configured properly for direct handoff, and are versions of Oracle that support direct handoff.
TNS-12516: TNS:listener could not find available handler with matching protocol stack
Cause: None of the known and available service handlers for the given SERVICE_NAME support the client's protocol stack: transport, session, and presentation protocols.
Action: Check to make sure that the service handlers (for example, dispatchers) for the given SERVICE_NAME are registered with the listener, are accepting connections, and that they are properly configured to support the desired protocols.