ORA-00472 disconnects from oracle database

I am running Oracle7 version ( Sqlnet v2.3) on a Compaq Proliant 6000 running Windows NT4 Server.  Over the last three weeks I have had three occurances of sudden disconnects from the database by all clients.  When you attempt to relog in you get a read failure.  The error that is reported is ORA-00472 which the error documentation states as the following:

ORA-00472      PMON process terminated with error

Cause:      The Process Monitor process terminated abnormally.
Action:      Check the accompanying messages, if any, and the background process trace file. Correct the problem mentioned in the other messages. Then shut down and restart the instance. If the trace file mentions any other background process messages, check the trace file for the mentioned process until the root message is found.
Copyright (C) 1995, Oracle Corporation

The only thing I can do is cycle the server.  Any ideas  on what is causing it ???   On two of the three occasions a backup/verify  was in progress (Backup Exec v7 - Oracle Addon forthcoming) but backups are run every day and this has only occurred three times.
When you look in the event log you see many lines like these:
6/17/98      2:06:21 AM      ORACLE7.orcl      Warning      None      16      N/A      NSCC      Instance orcl has been terminated.
6/16/98      2:04:20 AM      ORACLE7.orcl      Error      None      23      N/A      NSCC      ReadFile() failure.

I know virtually nothing about Oracle but I would like to correct/avoid this problem.
Any help would be appreciated.
Who is Participating?
poncejuaConnect With a Mentor Commented:

If you're runing an export backup in shared mode, probably the lock manager is failing, probably due to insufficient resources. Reference the readmedlm.doc under $ORACLE_HOME/pso/doc/readmedlm.doc. This document
gives a formula to correctly calculate the number of lock manager resources which need to be specified when starting the DLM on each node.

Oracle will provide help with this.  

They will ask for your dump files and the configuration information.  The dump files will be in a location specified in the  config.ora (background_dump_dest).  

I've had similar problems with PMON etc.  In our case it was occuring regularly for no obvious reason when the DB was being accessed by a Visual Basic program using ODBC or when Designer/2000 was performing a reconciliation.  I was advised to turn off any multi thread server options I was using (init.ora parameters beginning with the letters "mts").  

Hope this is of some use!
scalpyAuthor Commented:
Thanks guys.  I have purchased the Seagate Backup Exec Options Agent for Oracle Server for Windows NT.  The backup option seems to have solved the problem.
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.