select for update is not working in concurrent process

[Felix]

i have three process running concurrently , and i have select for update in my application , so that only one process get a row lock at single point of time. this is working fine when the process are running at different time(even milli secs different). to my surprise there were two process got lock of same rec , when i debug... i found the two process started at same point (no milli secs diff) , this might happen. and processed the row !!!. how to avoid from locking the row even the two process running at same time with no milli sec difference.\[code\]SELECT * FROM (SELECT column1, column2 , column3 , column4 WHERE column1 = ?) WHERE ROWNUM = 1 FOR UPDATE\[/code\]Thanks