Hmmm I wasn't really aware that you could turn them off. Thought you "got them" starting with 9i. I had a 9.2.0.4 database that had optimizer_features set to 8.0.4 When I removed the optimizer_features param, I had a query go from 5 minutes to 6 hours. It started using a skip scan. The problem was that the developer went view-crazy. The query went something like "select * from tab1 minus select * from tab2". But tab1 and tab2 were really views, and one of those contained yet another view. Under 8.0 everything was date-driven, which worked. But in 9i Oracle decided to outsmart itself and use another index. Oracle could not see the "big picture" because rather than a nice query that it could optimize, everything was hidden in the views. Only time I've seen a problem, but it was a biggie. Others have raved about skip scans. I just always seem to get the flaky queries . . . I'd say go for it, but watch for the sucker-punch. Barb On Wed, 29 Dec 2004 13:47:12 -0500, Mladen Gogala <mgogala@xxxxxxxxxxxxxxxxxxxx> wrote: > Is anybody using index skip scan feature? What would be a situation in which > the feature should be used? I have a SQL statement, part of ETL process > that I > have to tune. The initial reuslts are encouraging although not > dramatic. Does anybody > else have any type of practical experience with skip scans and index_ss > hint? > > -- > Mladen Gogala > Oracle DBA > Ext. 121 > > -- > //www.freelists.org/webpage/oracle-l > -- //www.freelists.org/webpage/oracle-l