Comments on: Event Histograms – 2

By: Event snapshots « Oracle Scratchpad

Event snapshots « Oracle Scratchpad — Mon, 16 Jun 2008 09:12:41 +0000

[...] by Event Histograms – 2 « Oracle Scratchpad — June 16, 2008 @ 9:11 am UTC Jun [...]

By: Event Histograms « Oracle Scratchpad

Event Histograms « Oracle Scratchpad — Fri, 13 Jun 2008 19:54:57 +0000

[...] Event Histograms Filed under: Troubleshooting — Jonathan Lewis @ 8:44 pm UTC Jan 10,2007 [Forward to Part 2] [...]

By: Jonathan Lewis

Jonathan Lewis — Mon, 28 May 2007 11:26:18 +0000

David, Long live statspack !

By: David Lopez

David Lopez — Mon, 28 May 2007 11:02:03 +0000

In AWR reports there is no event histogram statistics!

By: Jonathan Lewis

Jonathan Lewis — Fri, 02 Feb 2007 17:37:05 +0000

Someone called Rita left a question asking if I could elaborate on the problems these two sites had. Unfortunately this got marked as spam, and I deleted it by accident when clearing the spam list.

So – the first site was literally just working too hard. Modifying a couple of indexes to better precision, and fixing a couple of very popular queries, then adding on a stack of extra disks was sufficient to deal with the overload. If you could see the whole histogram, you would see the classic “long tail” indicative of typical queueing load.

In the second case, a hardware problem made some of the disc response times very bad. It was a long time ago amd I don’t remember the details but it might have been a microcode error in the caching algorithms. The problem went away after the disc manufacturer installed a patch. You get a hint about this because the histogram suggests a bell curve centred on the 8ms area, with a sudden spike and tail off further to the right.

By: Noons

Noons — Thu, 01 Feb 2007 02:55:30 +0000

3.4 Mwaits on dfsr in one hour! Man, that reminds me of the RH3/9ir2 database at my previous job…