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Don Burleson Blog 







ORA-12516 tips

Oracle Database Tips by Donald BurlesonFebruary 14, 2015

Question:  I am getting this ORA-12516 error:

ORA-12516, TNS: listener could not find available handler with matching protocol stack' When Running the RunETL Process

 Can you explain a solution to the ORA-12516 error?  I have two application servers (Web Logic) and I am getting the ORA-12516 from only one of the application servers.

Answer: The oerr utility shows this for the ORA-12516 error:

ORA-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 (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.

You have to check why the listener was rejecting the connection and do nslookup for the saecopq20(DNS name),and see what and all IP address are mapped to the DNS, and check to see those IP address are listening.

Please refer to MOSC Note 1100982.1 and MOSC note 240710.1, notes that talk about the TNS-12516 occurring intermittently in the clients.

This is because the listener, which relies on Automatic Instance Registration (or AIR) for configuring the services the listener should listen for, gets a lot of client requests and thus runs out of handles to open with the database server and hence this error.

Possible fixes for the ORA-12516:

1.) As a Fix, increase the value for PROCESSES in the init.ora file of the instance.

2.) You can have static registration for this instance by having a SID_LIST in the listener.ora file in addition to the automatic instance registration.

Also note bug Bug 8232287 - PMON stops registering its services (ORA-12516 errors) [ID 8232287.8]

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