Runaway SMON process on 7.2.2.3?

I am currently running Oracle 7.2.2.3 under HP/UX 10.01, on a dual processor HP 9000/K200. We are experiencing problems whose biggest symptom is an SMON process which is using excessive amounts of CPU time (> 90 minutes/day). Our database contains several thousand tables which are queried frequently, selecting a few records at a time. This means there is large turnover in our shared pool. I know the SMON process coalesces free space. Having read about bug #318582 and shared pool memory fragmentation problems, I wonder if the overactive SMON process is a symptom of this bug.

I have seen occasional ORA-4301 errors, but nothing persistent. Normally our SMON process wakes up every 5 minutes and utilizes 2% to 3% of available CPU for a few seconds. After heavy querying, SMON takes up >98% of available CPU for 5 minutes or more. This in turn has two noticeable results. First, it blocks other Oracle processes with an ST lock, until SMON has completed its work. Second, it dramatically slows down all system users, even those not using Oracle. Eventually everything completes normally, just much more slowly than expected. Adjustments in many initialization parameters have not yielded any improvement. The SMON process also becomes hyperactive if I flush the shared pool. Has anyone seem similar symptoms or know of a likely cause? I have had a TAR open for several weeks without any answers.

Thanks!

• Andy Zitelli, Silicon Systems, Inc.