The truth behind UPDATE STATISTICS...

H'ok, you probably think this is a dumbarse question, but apart from the various system catalogs, what else does UPDATE STATISTICS update? If I run two identical SELECTs under ISQL on two simultaneous sessions, having executed an UPDATE on one session, the optimizer takes different index paths (result being either an instant response on the 'UPDATEd' session or five minutes plus on the other). I've checked the obvious things like colmin, colmax and the values stored on sysindexes and they are identical in both sessions. UPDATE STATISTICS must be doing something else, but what? The box in question is an HP 9000/857 running 9.08 BLS & Online/Secure v5.00UD4 with a single label instance. --------------------------------------- Rizzo rizzo@fourgee.demon.co.uk ---------------------------------------