Oracle-L: Oracle shadow processes run amok after system clock changed

From: Deborah Lorraine <dlorraine_at_ucdavis.edu>
Date: Tue, 17 Dec 2002 15:34:21 -0800
Message-ID: <F001.0051C1C5.20021217153421@fatcity.com>

For those of you DBA's with a UNIX/SYSADMIN background, what do you think of this problem:

For a yet-to-be-explained reason, the system clock on our sun database server suddenly changed back 1 hour and 16 minutes sometime around 4 p.m. yesterday afternoon. The initial symptoms were that users could not log in to the database (we use kerberos for authenticating most user accounts which requires an accurate time), and we had an unusually high load average of 77! Once we finally figured out the clock was off and the sysadmin reset it, the load average did not change even though users could log in again. We then noticed 72 (of ~500) oracle processes in the run state, all evenly collecting CPU time, although database performance was good.

Some of these 72 processes were orphans and had no database process. Most had been doing simple selects, but not a single one was actually active in the database. Not all were kerberos-autenticated sessions. The only thing these processes had in common is that their process time stamps were in the hour period of that questionable time:

   oracle 11971     1  2 16:02:28 ?       18:05 oracleprod (LOCAL=NO)
   oracle 13335     1  2 16:19:40 ?       18:19 oracleprod (LOCAL=NO)
   oracle  9911     1  1 15:47:23 ?       18:18 oracleprod (LOCAL=NO)

...

After the clock was reset to the correct time, these processes did not clear out but when killed, the load returned to normal.

For the most part, Oracle is oblivious to the system clock setting so what could have caused the shadow processes to run amok? What could they be doing to generate CPU yet doing nothing in the database? Any ideas?

Thanks,

Debi

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Author: Deborah Lorraine
INET: dlorraine_at_ucdavis.edu

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