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

[CAS_2]

Hi

Some days ago, the clients connecting to my DB suddenly got hung for 15 minutes aprox... After those 15 min, all clients were alive back with no intervention.

No error message is found in alert log. No error message is found in syslog.log. No process died.

I scanned the listener.log and found a low connection rate: 3, 4 or 7 connections per minute (usually there are 50 connections per minute).

I also found the following error message in those 15 minutes period:

26-JUN-2006 12:14:56 * 12502
TNS-12502: TNS:listener received no CONNECT_DATA from client


I guess there might be a LAN problem but network team says no net problem was found.

What does that message mean ?
What do you think about this issue ?

[Peter Godron]

CAS,
you don't specify what version of oracle you are running.
TNS-12502 means thta your listener received a connect_string from a connection, which it did not understand.

Check your tnsnames.ora file.

Is there another program trying to use your listener port?

[CAS_2]

I tested the following:

telnet

After establishing connection, I close it.

This event causes the TNS-12502 error message in listener.log.