Sometimes, a "good" index causes exceptionally bad performance. We have a situation where if I add, what I "think" is, a good index on paper, the execution plan changes in such a way as to make subsequent queries perform horribly. The physical I/O looks good, the cost looks good, but the logical I/O goes berserk. Chris Taylor Sr. Oracle DBA Ingram Barge Company Nashville, TN 37205 Office: 615-517-3355 Cell: 615-663-1673 Email: chris.taylor@xxxxxxxxxxxxxxx<mailto:chris.taylor@xxxxxxxxxxxxxxx> CONFIDENTIALITY NOTICE: This e-mail and any attachments are confidential and may also be privileged. If you are not the named recipient, please notify the sender immediately and delete the contents of this message without disclosing the contents to anyone, using them for any purpose, or storing or copying the information on any medium. From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Ram Raman Sent: Thursday, August 11, 2011 3:45 PM To: ORACLE-L Subject: How many is too many Listers, I am looking at a table in our system and it has 12 indexes, we are planning on adding another one. I am aware of the effects of having too many indexes, but in this case adding an extra index helps a certain query that runs slow. Other queries and most other operations against the table are acceptable too. I see a few tables like this; is there a number above which is considered a no-no when it comes to adding more indexes. PS. The tables and queries are structured in a way that seem to require several indexes - it is a third party product. TIA, Ram.