Not sure what platform or version of Oracle you're on, but I did run into something similar on
AIX with Oracle v126.96.36.199
. An overview is in
Note #3639594.8. It's a bug. Check the note to see if your
platform.version fits for this issue. Not sure if there's a patch
for this - we were in the process of upgrading to 188.8.131.52 and the
When PMON cleans up a dead process then it may notice an
in-progress "ALTER SYSTEM SET PARAMETER" command and assume
(incorrectly) that this was from the failed process. It may
then try to clean up the in-progress command and so conflict
with the running session performing the ALTER SYSTEM command.
This shows up as numerous "PMON failed to acquire latch, see PMON dump"
On 8/7/07, email@example.com <firstname.lastname@example.org> wrote:
Looking for ideas/comments/suggestions..........
We changed cursor_sharing from EXACT
to SIMILAR last Saturday morning at 6am.
Did that via an "ALTER SESSION
The environment is large (7TB) but not
very busy on Saturday morning.
We had cursor_sharing=similar in multiple
test environments, for many months without issue.
At 9:15am, we started to generated ora-04031
By 9:30am, we could no longer sign-on.
We ended up shutting down the middle-tier,
and deleting all of the
OS processes on the DB server, that
represented connections to the instance.
At that point, we were able to signon,
backout the change, and startup the middle-tier again.
In the alert log, we saw the ora-04031
errors, and also many (thousands) of messages saying
"PMON failed to acquire latch,
see PMON dump".
The PMON trace file show the same entry,
repeated thousands of times:
"PMON unable to acquire latch 2c4cb108
possible holder pid = 1000 ospid=42586708"
Any ideas on what happened would be