Comments on: Upgrade Argh

By: Jonathan Lewis

Jonathan Lewis — Tue, 27 Sep 2011 22:53:38 +0000

Just landed and got to the hotel.
Strangely the problem doesn’t apply to the recycle cache, or if you use the default cache with the nocache option.

By: Jonathan Lewis

Jonathan Lewis — Tue, 27 Sep 2011 08:21:10 +0000

We have to change parameters some time – otherwise we don’t get all the “new, improved” bits.
The problems appear when your pre-launch testing doesn’t happen to pick up the issue.
This particular extreme case was during a materialized view refresh – and it’s easy for a job like that to not be run through a test suite (think of the number of times OTN has seen requests from people who discovered too late the side effects of the ‘atomic’ refresh kicking in on a process that had worked perfectly for years).

By: Jonathan Lewis

Jonathan Lewis — Tue, 27 Sep 2011 08:18:35 +0000

It seems as if Oracle used serial direct path read because the tables were assigned to a non-existent keep cache.
I didn’t check to see what would happen if they were defined as NOCACHE (or if they were assigned to a non-existent recycle cache).
I’ve got my laptop with me and a 13 hour journey ahead of me, so I might check that out – but I’m sure there are plenty of readers who will beat me to it before I land.

By: Hemant K Chitale

Hemant K Chitale — Tue, 27 Sep 2011 08:00:50 +0000

Excuse my obtuseness… Oracle did used Serial Direct Path Read for these tables not because they were “sufficiently large” but because they were “not to be cached” ? Would this behaviour be similar if we set “NOCACHE” for these tables ?

By: laimis (lnd)

laimis (lnd) — Tue, 27 Sep 2011 06:42:50 +0000

That´s a good one. The “Top N” thought is to exclaim why one trusts automated things in the first Oracle release ?
But the next thought is: why were parameters changed during upgrade in the first place ? Just to give a try ?
Discarding the established methods results in well hidden issues which require ingenious minds like that of Jonathan. Which is good for him and for other DBA’s but really shatters confidence in Oracle…