I’ve seen some very good information posted in this feed which combines blog postings from many different Oracle performance experts who are part of what is called the “Oak Table”
I’ve been using Internet Explorer to keep track of new posts in its “Feeds” section of (more...)
In my forum discussion about free buffer waits I came across a term that I didn’t understand: “inode lock contention”. I’m pretty sure I had seen this same term years ago on one of Steve Adams’ pages on IO. But, I didn’t really understand what the term meant (more...)
I just read this post about a new patch that will allow you to affect the way the optimizer calculates clustering factor and hence how likely it is to choose a particular index for a query plan.
Pretty cool. I haven’t tried it, but it looks (more...)
This is a good web site with Oracle internals information:
I’ve benefited from this one for years.
In my previous post I explained that setting db_writer_processes=1, dbwr_io_slaves=32 made a 2-3 times reduction in run time of my test of 15 concurrent updates.
Further testing has shown that an even greater improvement – really 10 times – can be made by switching to direct IO and maxing out (more...)
I’m working on an HP-UX system that doesn’t have asynchronous I/O configured and I’m getting a bunch of “free buffer waits” which indicates that the DBWR processes are having trouble writing updated blocks from memory to disk fast enough. Some preliminary testing I’ve done implies that I should change (more...)
I used this query to debug some updating issues on a table:
You can use DBA_HIST_ACTIVE_SESS_HISTORY to show details about the PeopleSoft operator id (OPRID) and which part of the online application they were in. I was just looking at a Query Manager issue and found that DBA_HIST_ACTIVE_SESS_HISTORY populated these three columns with PeopleSoft specific information like this:
I attended John Beresniewicz’s Active Session History (ASH) talk at Collaborate 13 on Monday. One simple point from it was that he commonly sees queries of the ASH views that use the TIME_WAITED column incorrectly and result in incorrect results. The ASH views are V$ACTIVE_SESSION_HISTORY and DBA_HIST_ACTIVE_SESS_HISTORY.
Well, I’m giving this talk related to Exadata at the Collaborate 13 usergroup conference on Monday. I’ve spent a lot of time – probably too much time – preparing the slides and practicing the talk. I first gave this talk a year ago at our office and then (more...)