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:
ORCL = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 10.10.10.10)(PORT = 1521)) ) (CONNECT_DATA = (SERVICE_NAME = ORCL) ) )It sounds like you're missing some information.
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This was first published in June 2003