It may be that Oracle has incorrect statistics concerning your I/O system, or even if those statistics are good, has still misjudged its capabilities. It may be the OS statistics were gathered at an inappropriate time. I am of the opinion that Oracle still overrates full table scans as compared to index lookups. There is an initialization parameter which addresses this. optimizer_index_cost_adj I would not change this parameter unless you are sure that the OS statistics were taken under an appropriate load, and the non-optimal FTS choices be made by the optimizer are noticeably slowing the system. Obviously changing the parameter can lead to an index being used when an FTS is optimal. -----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Orlando L Sent: Monday, August 15, 2011 9:38 AM To: Ric Van Dyke Cc: oracle-l@xxxxxxxxxxxxx Subject: Re: Hints Thank you Ric and others. I have few queries that run slow, but I have to force them to use indexes. With the use of indexes they run much faster, with statistics present. I am left with the classic question of why is the optimizer not using my indexes and why do I have to force it. -- //www.freelists.org/webpage/oracle-l