Important Oracle Errors Interview Questions
Q – 1 ORA-12502: TNS:listener received no CONNECT_DATA from client?
Ans- Cause:
No CONNECT_DATA was passed to the listener.
Action:
Check that the service name resolved from
TNSNAMES.ORA has the CONNECT_DATA component of the connect descriptor.
Q – 2 ORA-12504: TNS:listener was not given the SID in CONNECT_DATA?
Ans- Cause:
The SID was missing from the CONNECT_DATA.
Action:
Check that the connect descriptor corresponding to the service name in TNSNAMES.ORA has an SID component in the
CONNECT_DATA.
Q – 3 ORA-12505: TNS:listener does not currently know of SID given in connect descriptor?
Ans- Cause:
The listener received a request to establish a connection to a database or other service. The connect descriptor received by the listener specified a SID 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.
Q – 4 ORA-12508: TNS:listener could not resolve the COMMAND given?
Ans- Cause:
d by incompatible Oracle Net or Net8 versions. Do not include in error manual.
Action:
This is not seen in normal use of Oracle Net.
Q – 5 ORA-12509: TNS:listener failed to redirect client to service handler?
Ans- Cause:
The dispatcher terminated unexpectedly
Action:
Attempt to connect again and if the same error occurs, contact the DBA to check the state of the dispatchers for this SID. If the problem persists, turn on tracing in the listener to determine the TNS error caused by the redirect.
Q – 6 ORA-12510: TNS:database temporarily lacks resources to handle the request?
Ans- Cause:
The dispatchers appear to be busy handling other requests.
Action:
Attempt the connection again. If error persists, ask the DBA to increase the number of dispatchers and/or dispatchers’ limit on number of connections/sessions that they can accept.
Q – 7 ORA-12511: TNS:service handler found but it is not accepting connections?
Ans- Cause:
The dispatchers notified the listener that they temporarily do not accept new connections.
Action:
Attempt the connection again. If error persists, contact the DBA to check the state of the dispatchers and/or ask him to increase the number of dispatchers.
Q – 8 ORA-12513: TNS:service handler found but it has registered for a different protocol?
Ans- Cause:
The dispatchers registered for this service are connected to the listener by way of a different network protocol than that of the client.
Action:
Contact the DBA to register a dispatcher on your protocol.
Q – 9 ORA-12514: TNS:listener does not currently know of service requested in connect descriptor?
Ans- Cause:
The listener received a request to establish a connection to a database or other service. The connect descriptor received by the listener specified a service name for a service (usually a database service) 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.
Q – 10 ORA-12515: TNS:listener could not find a handler for this presentation?
Ans- Cause:
None of the listener’s known service handlers are registered as supporting the presentation protocol required by the connecting client.
Action:
Check that the destination service is configured to accept the presentation protocol.
Q – 11 ORA-12516: TNS:listener could not find available handler with matching protocol stack?
Ans- 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 (e.g. 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.
Q – 12 ORA-12518: TNS:listener could not hand off client connection?
Ans- 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 problem persists, call Oracle Support.
Q – 13 ORA-12519: TNS:no appropriate service handler found?
Ans- 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.
Q – 14 ORA-12520: TNS:listener could not find available handler for requested type of server?
Ans- 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.
Q – 15 ORA-12521: TNS:listener does not currently know of instance requested in connect descriptor?
Ans- Cause:
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.