Comments on: Slow rman Backups? Check This Out

By: Mila

Mila — Thu, 01 Oct 2009 20:11:11 +0000

Incorrect query-
If you have materialized views , make sure the parameter query_rewrite_enable set to FALSE.
This was my case with CBO and RBO. CBO was choosing mview instead of table.

By: Raj Thukral

Raj Thukral — Fri, 04 May 2007 12:47:04 +0000

Chris
There’s been a few bugs with queries in oracle, but I doubt thats a function of the CBO. You probably need to take a closer look at your query – its likely the order of joins changes the results, which usually means a bad query or a bad join somewhere. Using the rule hint can change the order of joins.
–Raj.

By: chris dittaro

chris dittaro — Thu, 03 May 2007 21:42:42 +0000

We are having some scary things happening with incorrect query results when running CBO-based statements in our 10G db. When we run the same query ruled-based, it returns the correct result. Tried to add the system parameter:
set “_cost_equality_semi_join”=false as a workaround (from the Bug fix doc) but it didn’t change a thing.
does anyone have an answer/fix for this one?

By: Alex Gorbachev

Alex Gorbachev — Wed, 24 Jan 2007 22:15:19 +0000

Thanks to Dmitry Bogomolov, our Russian readers can enjoy a translated version.

By: vidya

vidya — Wed, 24 Jan 2007 19:09:34 +0000

Raj,
this is scary , I really thought that RULE was totally out in 10g…..i hope there has been no issues with query performances

By: Fairlie

Fairlie — Thu, 18 Jan 2007 05:52:33 +0000

What amazes me is that the 10G Docs say that RBO is desupported and the workaround in the bug is to use RBO …lol :-)
I had another issue a couple of days ago where a query gave incorrect results with CBO but the correct results with the RBO.

By: Jsffar Hussain

Jsffar Hussain — Wed, 17 Jan 2007 06:43:04 +0000

But, Raj, the note says that the issues is when ‘RMAN SLOW PERFORMANCE DURING RESITER DATABASE/OPEN RESETLOGS’ Is the same with typical backups as well?

Jaffar

By: Don Seiler

Don Seiler — Wed, 17 Jan 2007 02:29:43 +0000

Offhand, do you think this would have any effect on restore/duplication times? My duplications take ~ 8 hours as well.

By: Don Seiler

Don Seiler — Wed, 17 Jan 2007 02:00:03 +0000

OMFG. I just ran the two test queries in the “REDISCOVERY INFORMATION” section of the bug. Without the rule hint, the query ran in 1:15:24.79. With rule hint, it ran in 00:00:00.14. I even tested new ranges to make sure nothing was cached.

My level 0 backup of my ~ 840 gb database has been taking over 9 hours. I can’t wait to see what this does.

By: Noons

Noons — Tue, 16 Jan 2007 22:11:00 +0000

very useful stuff to know.
thanks, Raj!