Cursor_sharing=similar.....failed -- daniel hubler 2007-08-07
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