Category Archives: Uncategorized

I was working on some disk performance problems and came across a simple way to test the latency or delay built into the networks that connect my database servers to their disk storage.  All I have to do is read … Continue reading →

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” http://www.oaktable.net/feed/blog-rss.xml (NO LONGER EXISTS) I’ve been using Internet Explorer to … Continue reading →

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, … Continue reading →

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. http://richardfoote.wordpress.com/2013/05/08/important-clustering-factor-calculation-improvement-fix-you/ Pretty cool.  … Continue reading →

This is a good web site with Oracle internals information: http://www.ixora.com.au/notes/ (NO LONGER EXISTS) I’ve benefited from this one for years. – Bobby

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 … Continue reading →

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 … Continue reading →

I used this query to debug some updating issues on a table: select ss.DATAOBJ#, sn.END_INTERVAL_TIME, ss.DB_BLOCK_CHANGES_DELTA, ss.PHYSICAL_WRITES_DELTA from DBA_HIST_SEG_STAT ss, DBA_HIST_SNAPSHOT sn, DBA_HIST_SEG_STAT_OBJ so where so.OWNER=’MYUSER’ and so.OBJECT_NAME=’PLAN_TABLE’ and so.OBJECT_TYPE=’TABLE’ and ss.OBJ#=so.OBJ# and ss.DATAOBJ#=so.DATAOBJ# and ss.snap_id=sn.snap_id order by ss.snap_id,ss.DATAOBJ#; This … Continue reading →

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 … Continue reading →

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.  … Continue reading →