Cause
Blocking sessions occur when one sessions holds an exclusive lock on an object and doesn’t release it before another sessions wants to update the same data. This will block the second until the first one has done its work.
Please execute the below query to find the blocking sessions and kill if necessary.
Solution
col WAIT_CLASS FOR a12;
SELECT blocking_session,
sid,
serial#,
wait_class,
seconds_in_wait,STATUS
FROM
v$session
WHERE
blocking_session IS NOT NULL
ORDER BY
blocking_session;
SELECT blocking_session,
sid,
serial#,
wait_class,
seconds_in_wait,STATUS
FROM
v$session
WHERE
blocking_session IS NOT NULL
ORDER BY
blocking_session;
