Tuesday, May 01, 2018

Session Blockers In DB After OS Panic or DB Aborted


   Due to OS panic or we did shutdown abort on oracle DB. DB was started well.
   However in a while , there were quite many blocking sessions ( enq: TX - row lock contention)  which caused Application performance issues


From blocking sid  and run sql checking, we found the blockers were idle sessions and had  such wait event: "SQL * NET message from client ".
   About how idle sessions can be blockers , please refer stackexchange link
   So it turns out that the unreleased locks of last sessions before OS panic and shutdown abort will remain in the DB. After DB restarts, the locks are still in place.


     We need to clear the blockers manually or bounce the MT to refresh all the connections.

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