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Resolving the TNS-12502 error

I have an Oracle database with a server IP of, and it also has a virtual IP of The virtual IP is the way some of my clients must hit the database with the use of tnsnames.ora(host= instead of the actual IP address. Those clients are receiving 12502 errors and the listener log is showing these errors also. Is there anything special I need to do?

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Here's what the Error Messages guide says about the TNS-12502 error:

TNS-12502 TNS:listener received no CONNECT_DATA from client
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.

So, the first step is to check your TNSNAMES.ORA file that the clients are using and verify that it looks something like this:

      (ADDRESS = (PROTOCOL = TCP)(HOST = = 1521))
It sounds like you're missing some information.

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This was first published in June 2003

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