On Tue, Dec 15, 2009 at 7:22 AM, Syed Jaffar Hussain <sjaffarhussain@xxxxxxxxx> wrote: > Hi everyone, > > The following simple join query on one of our business critical RAC > databases with two instances was frequently leading into a dead lock > situation ultimately a causing database hang scenario: > > SELECT u.u_user_id, u..u_mcr_cust_id > FROM table1 U,table2 A > WHERE > A.UCS_CHNL_ID = :b1 AND A.UCS_LOGIN_NAME = :b2 AND A.UCS_USER_ID = > U.U_USER_ID FOR UPDATE > As I understand this query condition is based on user login name - When exactly this dead lock happen ? when this same user is trying to login twice from two different machines ? Maybe there are some old, unused and not committed sessions ? regards, Marcin Przepiorowski -- //www.freelists.org/webpage/oracle-l