Re: Questions about SQL Plan Management (answered)
From: Wolfgang Breitling <breitliw_at_centrexcc.com>
Date: Thu, 3 Jul 2014 17:04:12 -0600
Message-Id: <4C082D0B-CFF9-4018-87C6-6703FD8A9C61_at_centrexcc.com>
It only triples the parsing overhead if the plan ( phv ) can not be reproduced at first attempt. The second parse trip guarantees plan stability unless the environment has changed to such a degree that the stored hints do not reproduce the same PHV. That is something the old outlines didn't have. SPM has another advantage over the old outlines: it can be used to rule out undesirable plans, e.g. the case where an unfortunate bind value at first parse ruins the plan for everybody following.
Date: Thu, 3 Jul 2014 17:04:12 -0600
Message-Id: <4C082D0B-CFF9-4018-87C6-6703FD8A9C61_at_centrexcc.com>
It only triples the parsing overhead if the plan ( phv ) can not be reproduced at first attempt. The second parse trip guarantees plan stability unless the environment has changed to such a degree that the stored hints do not reproduce the same PHV. That is something the old outlines didn't have. SPM has another advantage over the old outlines: it can be used to rule out undesirable plans, e.g. the case where an unfortunate bind value at first parse ruins the plan for everybody following.
Wolfgang Breitling
breitliw_at_centrexcc.com
On 2014-07-03, at 3:49 PM, Iggy Fernandez <iggy_fernandez_at_hotmail.com> wrote:
> A corollary seems to be that SPM triples the parsing overhead while not improving the stability guarantee compared to Oracle 8.0 stored outlines.
>
-- http://www.freelists.org/webpage/oracle-lReceived on Fri Jul 04 2014 - 01:04:12 CEST