Re: interpret vacuum verbose output

On Thu, 2003-06-05 at 04:54, Peter Childs wrote:
> On Wed, 4 Jun 2003, Shankar K wrote:
>
> > hi all,
> >
> > I'm trying to evaluate the frequecy to run vacuum
> > analyze on key tables. so if anyone could help me to
> > interpret the output of vacuum analyze verbose output
> > that would be great. below is the output of one of our
> > major indexes.
> >
> UnUsed: Number of Records In Table not in use currently. (I think vacuum
> full should remove these)

yes

> Changed: Number of Records Changed (Not sure)

Number of Pages Changed

> Keep: Number of Records to Keep (Not Sure)

Correct. Usually these are tuples that are currently being accessed
within a transaction.

> If deleted gets too big you should be vacuuming more often
>

not really, unused is far more significant for that. You might say if
deleted is too small, you might want to vacuum less frequently.

> If unused gets too big try and increase your fsm size.
>

if it gets too big, it's a sign you're not vacuuming enough.
if it gets way too big, you need to do a vacuum full.

note recommendations on deleted and unused both assume you have
increased your fsm settings appropriately.

also note that in pre-7.4 releases, vacuum cannot remove dead pages
within indexes, so if your indexes grow to large you will need to
REINDEX

Robert Treat

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