Thanx a lot for ur reply Mr.Cary . I have a few more questions please ! These are a few lines from my trace file for a simple query. *** SESSION ID:(10.12) 2004-03-29 18:40:55.421 PARSE #1: tim=31028556368 EXEC #1: tim=31028575483 1.The difference between PARSE and EXEC is ( 31028575483 - 31028556368 ) = 19115 . is it so many micro seconds elapsed ? 2.The timestamp in " *** " line is the nearest one. so how many seconds have the clock advanced by during the PARSE and EXEC line ? Can you explain me please ? Thanx again. Regards, Prem.