Thanks for response. So Hrvoje, if we perform the RMAN backup without Networker (from Oracle user command line), and we succeed then it means that this is a Networker issue, right?

This seems to be Oracle issue now. Oracle says:

Cause: A call to Oracle was attempted when no connection was established.
Usually this happens because a user-written program has not logged on. It may
happen if communication trouble causes a disconnection. In addition, this
message could occur when ALTER SYSTEM KILL SESSION or ALTER SYSTEM
DISCONNECT SESSION were issued with the IMMEDIATE qualifier because,
in those cases, the client¿s connection to the database is terminated without
waiting for the client to issue a request.
Action: Try again. If the message recurs and the program is user written, check
the program.

You may wish to check for more via Metalink site.

If you perform backup by running rman cmdfile you are still using NetWorker's library. The only thing not used is nsrnmo script which is there for scheduled backups only.

hi;

perhaps it may help you

http://www.orafaq.com/usenet/comp.databases.oracle.server/2000/09/13/0069.htm

Thanks..Kenan this is a very old document, it might be useful but here's Win2003SP1. I'll the check the mentioned TcpMaxDataRetransmissions variable.