Вот что говорит по этому поводу Instant Messages:

ORA-03113 end-of-file on communication channel

Cause: An unexpected end-of-file was processed on the communication channel. The problem could not be handled by the Net8, two task, software. This message could occur if the shadow two-task process associated with a Net8 connect has terminated abnormally, or if there is a physical failure of the interprocess communication vehicle, that is, the network or server machine went down.

Action: If this message occurs during a connection attempt, check the setup files for the appropriate Net8 driver and confirm Net8 software is correctly installed on the server. If the message occurs after a connection is well established, and the error is not due to a physical failure, check if a trace file was generated on the server at failure time. Existence of a trace file may suggest an Oracle internal error that requires the assistance of customer support.