PL/SQL lock timer

I was looking through V$SYSTEM_EVENT on an Oracle 11.2 production database (as you do) and I noticed that it had waited for exactly 1 second on the PL/SQL lock timer event. Apparently this is the amount of time a database has been waiting for sessions which have been told to sleep by their application. I decided to check this out so I started a new session, slept for 6.7 seconds then looked to see how long my session had been waiting on this event:

SQL> conn /

Connected.

SQL> exec dbms_lock.sleep(6.7);

 

PL/SQL procedure successfully completed.

 

SQL> select time_waited/100

  2  from v$session_event

  3  where event = 'PL/SQL lock timer'

  4  and sid = (select distinct sid from v$mystat)

  5  /

 

TIME_WAITED/100

---------------

           6.71

 

SQL>