OIC(A) again

Issues with OICA/OIC (OPTIMIZER_INDEX_COST_ADJ/OPTIMIZER_INDEX_CACHING) parameters have already been mentioned many times. Recently I’ve noticed one more and I think I didn’t see this case somewhere else on the Internet so I’ll share it.

FBI trouble

In our application we extensively use a function-based index on an important table. Couple of days ago I’ve seen an interesting issue associated with this FBI, view and a GROUP BY query. I have to say I don’t have an explanation what exactly it is and how I should call it properly, hence just “trouble” in the subject line.

16K CR gets for UQ index scan? Easy. Kind of.

I planned to write on this for quite some time, but failed to do so. Sorry about that. Today I finally got time and desire to describe a situation from the title. It was observed on an Oracle 9.2.0.8 running Solaris SPARC; manifested itself as a severe CPU burning at 100% utilization with ‘latch free’ on the first place of the Top 5 wait events in Statspack report.

Extended statistics and function-based indexes

About a year ago I’ve discovered nice feature of Oracle 10gR2 CBO: to overcome an issue with calculated selectivity for predicates on multiple columns, it can use DISTINCT_KEYS of the available index. Couple of weeks ago the bug fix mentioned in the OTN thread actually helped to solve a performance issue of a query. And about a week ago I found that this fix doesn’t work with function-based indexes. So, this post is about it.

Custom treedump

Not a tree, actually 😉 Just dump. Index dump. Custom index dump 😀 with blackjack and hookers (c)
Check it out here if you haven’t seen this yet.

Index ITL

Jonathan Lewis wrote a series of posts on topic of Index ITLs (interested transaction list), how and when they become huge and make index bigger in size – see this post with links to several other articles. As it turned out in a recent thread on SQL.ru forum, one of possible solutions to the issue – calling ALTER index COALESCE – appears to be very limited in it’s appliance. Why? Because COALESCE doesn’t clean out ITLs of all index leaf blocks – most important, it doesn’t clean out ITL of the right-most index leaf block.