Re: vacuum confusion

(Apologies if this message comes twice - my imap server and mail client
had a little problem)...

I've just noticed that the v8 docs are MUCH better in explaining this
than the 7.4.6 docs that I'm using (since I'm using 7.4.6 in production).

Perhaps if the same texts

<QUOTE>
play=# VACUUM;
WARNING:  some databases have not been vacuumed in 1613770184 transactions
HINT:  Better vacuum them within 533713463 transactions, or you may have
a wraparound failure.
VACUUM
</QUOTE>

and warning

<QUOTE>
To be sure of safety against transaction wraparound, it is necessary to
vacuum every table, including system catalogs, in every database at
least once every billion transactions. We have seen data loss situations
caused by people deciding that they only needed to vacuum their active
user tables, rather than issuing database-wide vacuum commands. That
will appear to work fine ... for a while.
</QUOTE>

were added to the 7.4.x docs that would help others too.

Thanks

John Sidney-Woollett

John Sidney-Woollett wrote:
> Thanks Richard, I found the page too...
>
> However the implication (and my confusion) is that you need to vacuum
> your own databases only. It's not clear (to me) that you have to do the
> same for template0 and template1 as well.
>
> Perhaps when someone is updating the docs, something more explicit than
> this
>
> <OLD> Recommended practice for most sites is to schedule a database-wide
> VACUUM once a day at a low-usage time of day, supplemented by more
> frequent vacuuming of heavily-updated tables if necessary. (If you have
> multiple databases in a cluster, don't forget to vacuum each one; the
> program vacuumdb may be helpful.) Use plain VACUUM, not VACUUM FULL, for
> routine vacuuming for space recovery.</OLD>
>
> could be replaced by this
>
> <NEW> Recommended practice for most sites is to schedule a database-wide
> VACUUM once a day at a low-usage time of day, supplemented by more
> frequent vacuuming of heavily-updated tables if necessary. (If you have
> multiple databases in a cluster, don't forget to vacuum each one
> (INCLUDING template0 and template1); the program vacuumdb may be
> helpful.) Use plain VACUUM, not VACUUM FULL, for routine vacuuming for
> space recovery.</NEW>
>
> And perhaps an explicit reference to vacuuming template0/1 in the
> section on "Preventing transaction ID wraparound failures" would be
> helpful.
>
> I'll add a weekly cron job to vacuum these two template databases.
>
> Thanks for your help again.
>
> John Sidney-Woollett
>
>
> Richard Huxton wrote:
>
>> John Sidney-Woollett wrote:
>>
>>> Ah.., no we're not vacuuming template0 or 1.
>>>
>>> I didn't realise that the transaction ID would be stored here - I
>>> assumed that they'd be in our database.
>>>
>>> Do I need to need to (plain) vacuum, or vacuum full these template0
>>> and template1? And is this something that can be done once a week
>>> rather than every night (like our main database)?
>>
>>
>>
>> Ah! Found the section of the manuals - see "Routine Database
>> Maintenance Tasks" for details.
>>
>> AFAIK it's a simple vacuum and once a week is more than enough. The
>> manual recommends once every 500million transactions, though you can
>> leave it longer.
>>
>> --
>>   Richard Huxton
>>   Archonet Ltd
>>
>> ---------------------------(end of broadcast)---------------------------
>> TIP 6: Have you searched our list archives?
>>
>>               http://archives.postgresql.org
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org