Comments on: Fake Baselines

By: Jonathan Lewis

Jonathan Lewis — Wed, 29 Aug 2012 08:56:05 +0000

Timur,

Thanks for the question – and the comprehensive follow-up.
The tracing information is particularly useful.

By: Timur Akhmadeev

Timur Akhmadeev — Fri, 24 Aug 2012 12:06:22 +0000

Plan stability is not supported for multitable insert statements.

And the reason for such restriction comes from the fact such statement misses OUTLINE part in the cursor, and SPM ignores it and writes following to the trace

load cc: plan outline extracted
load cc: plan has empty outline, skipping it
load cc: plans total=0plans loaded=0

SQL Patch is also not an option for the same reason.

By: Timur Akhmadeev

Timur Akhmadeev — Fri, 24 Aug 2012 10:03:38 +0000

I've found how to enable tracing for SPM: SQL PLAN MANAGEMENT TRACING ID 789520.1 Looks like something is not OK with the type of this statement. I'll follow up on this if I find something interesting.

By: Timur Akhmadeev

Timur Akhmadeev — Fri, 24 Aug 2012 09:54:45 +0000

Hi Jonathan

do you know how to diagnose why DBMS_SPM doesn’t load plans from cache? Both plans are definitely in the cursor cache, but for some reason DBMS_SPM returns zero as a result. I tried both doing it myself with your approach and with coe_load_sql_baseline.sql script from SQLTXPLAIN. This is RAC 11.2.0.3.2 on Linux, I’m using same instance for sure; and problem SQL runs in the scheduler job. Thanks for any pointers.

By: One simple example about Oracle SPM | leborchuk

One simple example about Oracle SPM | leborchuk — Sun, 19 Aug 2012 09:52:10 +0000

[...] Johathan Lewis http://jonathanlewis.wordpress.com/2011/01/12/fake-baselines/ [...]

By: PK Problem « Oracle Scratchpad

PK Problem « Oracle Scratchpad — Thu, 12 Jul 2012 16:19:05 +0000

[...] look at the option for creating an SQL Plan Baseline for a modified version of the query, and then attaching that plan to this query. Let’s work on that idea in steps – first we’ll just try aggregating the object [...]

By: Subquery Factoring « Oracle Scratchpad

Subquery Factoring « Oracle Scratchpad — Tue, 14 Feb 2012 18:01:23 +0000

[...] the view and attach it to the version of the query with the inline view but without the hint. (See Fake Baselines for one possible method of doing this capture.) Share this:TwitterLike this:LikeBe the first to [...]

By: Enabling constraint in parallel « Timur Akhmadeev's blog

Enabling constraint in parallel « Timur Akhmadeev's blog — Wed, 16 Feb 2011 19:05:31 +0000

[...] issued by Oracle to validate a constraint will be parallel? If you want 100% guarantee, you can use baselines. I’ve tested this approach and it worked as expected. Here is a run-time plan which used a [...]

By: Aswath Rao

Aswath Rao — Wed, 19 Jan 2011 16:14:23 +0000

Hi Jonathan,

Thanks for the wonderful blog on the SQL Baselines.

Thanks
Aswath Rao

By: Jonathan Lewis

Jonathan Lewis — Sun, 16 Jan 2011 17:43:40 +0000

Marcin, Thanks for that - it's a useful point to highlight. Particularly relevant, probably, when trying to fake things while cursor_sharing is set to force or similar - which can, of course, also cause confusion with "explain plan" and stored outlines.