ORA-12521 TNS:listener does not currently know of instance requested in connect descriptor
This is an Oracle Database Server Message. This can be generated by the Oracle Database when running any Oracle program.
What is the cause of ORA-12521 from Oracle 10g ?
The listener received a request to establish a connection to a database or other service. The connect descriptor received by the listener specified in addition to the service name an instance name for an instance (usually a database instance) that either has not yet dynamically registered with the listener or has not been statically configured for the listener. This may be a temporary condition such as after the listener has started, but before the database instance has registered with the listener.
How to deal with ORA-12521 from Oracle 10g ?
- Wait a moment and try to connect a second time.
- Check which instances are currently known by the listener by executing: lsnrctl services <listener name>
- Check that the INSTANCE_NAME parameter in the connect descriptor specifies an instance name known by the listener.
- Check for an event in the listener.log file.
Contacting Oracle support services ?
Some messages recommend contacting Oracle Support Services to report a problem. Please go here for more information : Oracle Support.
Linked Error Messages
- ORA-12513 TNS:service handler found but it has registered for a different protocol
- ORA-12514 TNS:listener does not currently know of service requested in connect descriptor
- ORA-12515 TNS:listener could not find a handler for this presentation
- ORA-12516 TNS:listener could not find available handler with matching protocol stack
- ORA-12518 TNS:listener could not hand off client connection
- ORA-12519 TNS:no appropriate service handler found
- ORA-12520 TNS:listener could not find available handler for requested type of server
- ORA-12522 TNS:listener could not find available instance with given INSTANCE_ROLE
- ORA-12523 TNS:listener could not find instance appropriate for the client connection
- ORA-12524 TNS:listener could not resolve HANDLER_NAME given in connect descriptor
- ORA-12525 TNS:listener has not received client's request in time allowed
- ORA-12526 TNS:listener: all appropriate instances are in restricted mode
- ORA-12527 TNS:listener: all instances are in restricted mode or blocking new connections
- ORA-12528 TNS:listener: all appropriate instances are blocking new connections
- ORA-12529 TNS:connect request rejected based on current filtering rules