Re: Replication Syatem

Greg Smith <gsmith@gregsmith.com> writes:
> The model here assumes that you'll need that space again for the next time
> you UPDATE or INSERT a row.  So instead VACUUM just keeps those available
> for database reuse rather than returning it to the operating system.

> Now, if you don't VACUUM frequently enough, this model breaks down, and
> the table can get bigger with space that may never get reused.  The idea
> is that you should be VACUUMing up now unneeded rows at about the same
> rate they're being re-used.  When you don't keep up, the database can
> expand in space that you don't get back again.  The right answer to this
> problem is not to use VACUUM FULL; it's to use regular VACUUM more often.

Also, you need to make sure you have the FSM parameters set high enough
so that all the free space found by a VACUUM run can be remembered.

The less often you run VACUUM, the more FSM space you need, because
there'll be more free space reclaimed per run.

            regards, tom lane