You may want to check below http://kerryosborne.oracle-guy.com/2009/04/hidden-sql-why-cant-i-find-my-sql-text/ Sent from my mobile device On Dec 19, 2011 7:50 AM, "louis" <ylouis83@xxxxxxxxx> wrote: > Hi: Everyone > When I monitoring the system I found some sessions cause the > wait_event --------- i/o slave wait in a few seconds > > and I found the sql_id of these sessions is 38wm92jbxu0vf,but when I query > v$sql I found the sql_text is null > > who can explain these? and I guess this query is on a table with clob > column. > > > -- > //www.freelists.org/webpage/oracle-l > > > -- //www.freelists.org/webpage/oracle-l