Hi Ray > If I alter optimizer_features_enable to 9.0.1 at session level. > It does get almost same explain plan and same results. But customer > does not want to do that. Are you aware that you can set that specific parameter by adding a hint? I mean: /*+ optimizer_features_enable('9.0.1') */ I understand that somebody doesn't want to have the parameter changed at session/instance level, but with the hint it's really used only for that specific query. HTH Chris PS: The performance of 10gR2 is great! That said it isn't perfect yet ;-) -- //www.freelists.org/webpage/oracle-l