Re: Re: Why Size Of Data Backed Up Varies Significantly In SQL 6.5?

J.H.M. Dassen (Ray) wrote:
> Wendy <windy1a(at)yahoo(dot)com> wrote:
> >I backed up a database at night and noted the size to be about over 300MB.
> >The following morning, I again backed up the same database and found out
> >the size to be less than 100MB. There was no massive deletes by users
> >during that morning.
> >What would account to that vast difference in size?
>
> An automatically executed script (e.g. cron job) that ran a VACUUM on the
> database during the night.
>
> >I'm really worried about this database because I don't understand what is
> >happening here.
>
> Deleted table entries still occupy disk space; VACUUMing cleans them out,
> thereby shrinking the database's disk space usage.

What leads to the question if he's thinking that taking a tar
archive from the data directory is a proper way of backing up
a PostgreSQL installation. You can do so, but have to ensure
that the postmaster isn't running while doing it. And on
restore you're not able to get anything less than all
database of the entire installation. Better look at pg_dump
for backing up PostgreSQL.

Jan

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