The most common cause for the above error is an ungraceful
disconnection of a session from the oracle db while the db is currently running
a dml statement issued by that session. The error is recorded when oracle
attempts to reply back to the session with the results of the dml and cannot
access the session. Overall database operations are usually not affected.

An ungraceful disconnection could cause by but is not limited to any of the
following:
- the client machine crashed
- the network connection crashed
- the user exited the session improperly (not issuing the 'exit' command)
- the user application allows the user to exit the application without properly
terminating the session.

The above can cause problems with corrupted rollback segments if occurring on a
regular basis and is not addressed. This would require db recovery and
possibly a db rebuild (not a light matter)

PMON will usually rollback most transactions in the rollback segments for a
session if it finds that the session has been ungracefully disconnected, but
there is always a chance that it cannot and this will lead to rollback segment
corruption.



fix:

The dml and the user that issued the dml can be determined from the trace file.
The current dml is in the tracefile header section. The user can be found in
the process state dump of the trace. The process state shows the machine,
o/suser, and user for the session.

The DBA can use this information to determine what the user was doing at the
time and if there was an ungraceful exit from the session the user was
utilizing.

The DBA should then address the cause of the ungraceful exit to reduce the
possibility of reoccurance.