Re: Unexplained Major Vacuum Archive Activity During Vacuum

On 11/01/2012 10:28 AM, Kevin Grittner wrote:

> http://www.postgresql.org/docs/9.2/interactive/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND

I read that several times, and I still don't get how it applies to this
case. Based on my past experience with 8.2, and my understanding of 9.1,
I moved autovacuum_freeze_max_age up to 650M so we'd never get a mid-day
freeze. And the default for vacuum_freeze_table_age is 150M, which I
hadn't changed.

So here's what I don't get:

* A manual vacuum vacuums a table.
* If the age of that table is > 150M (by default), also freeze.
* Counters are reset to autovacuum_freeze_min_age or 0... eh.

If that's the case, the freeze bit shouldn't have affected us, because I
already basically crippled autovacuum from freezing anything. The
nightly vacuum would freeze because we do more than 150M transactions
per day.

So with the new settings, we've been effectively doing a VACUUM FREEZE
every night. And this has been going on for weeks without issue.

But last night? Total pandemonium. I suppose it could be related to the
market being closed for 2 extra days, but we kept running our accounting
jobs. The volume is just very suspicious.

Either I'm totally misunderstanding a fundamental issue, or something
still seems fishy here.

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas(at)optionshouse(dot)com

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