Please, advice how to optimize optimizer_index_cost and the other optimizer

Question

I need to tune my performance. I have too many db_file_sequential read due to index lookups. The tables are Large and indexes are also large. I would like to only cache the indexes that are actually used.
Please, advice how to tune optimizer_index_cost and the other optimizer_index parameters.
Thanks a lot,
MJ

Answer 1

Oracle will only cache blocks from objects that are used. I'm not sure, therefore, what it is you are trying to cache (or not cache) here.
What version of Oracle are you using? Assuming you're using 9i or later, gathering system statistics is generally preferrable to adjusting optimizer initialization parameters.
You are also in the somewhat unique position of, apparently, complaining that the CBO is using too many indexes rather than doing full table scans. While it is certainly true that full table scans may be more efficient than index lookups, it is pretty rare for the CBO to erroneously use indexes when it shouldn't-- it tends to be much less index hungry than the RBO was, for example. It sounds like you likely have inefficient SQL that needs to be tuned, not that you have initialization parameters to tune.
Justin
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC