Re: Having trouble with backups (was: Re: Crash Recovery)

Carlos Moreno <moreno(at)mochima(dot)com> writes:
> And the second (and intriguing) problem: whenever I run pg_dump,
> my system *freezes* until pg_dump finishes. When I say "system",
> I mean the software that is running and sending data to the PG
> database.

Other people have responded on the assumption that this is a performance
problem, but you should also consider the possibility that it's bad
coding of your application software. Does your app try to grab
exclusive table locks? If so, it'll sit there waiting for the pg_dump
to complete. pg_dump only takes ACCESS SHARE lock on the tables it's
working on, which is the weakest type of lock and does not conflict with
most database operations ... but it does conflict with ACCESS EXCLUSIVE
lock requests.

regards, tom lane