Investigating Enqueues Burns CPU Cycles

March 30, 2011 If you take a look at the Oracle Database Performance Tuning Guide, you will find the following SQL statement to help identify the session waiting in an enqueue and the session that currently prevents that session from continuing: SELECT DECODE(request,0,'Holder: ','Waiter: ') ||           sid sess, id1, id2, lmode, request, type    [...]