Обсуждение: Taking databases offline

Hi!

Is it possible (and safe) to move database files to other location while
server is working? I had to move one to another volume/path and 'sym-linked'
it to old dir. But had to shutdown server first. So my question (and
suggestion) is to consider:

ALTER DATABASE <dbname> { OFFLINE [ { WAIT | IMMEDIATE }] | ONLINE };

Taking db offline with IMMEDIATE disconnects all sessions, with WAIT
option... waits for all sessions to disonnect, with no options - fails if
anyone is connected to database; then file system actions are allowed (like
in my case). After ALTER... ONLINE normal use of database is restored.

Waitng for comments,

Mariusz Czulada

"Mariusz Czu�ada" <manieq@idea.net.pl> writes:
> Is it possible (and safe) to move database files to other location while
> server is working?

No.  Shut down the postmaster first.

> But had to shutdown server first. So my question (and
> suggestion) is to consider:
> ALTER DATABASE <dbname> { OFFLINE [ { WAIT | IMMEDIATE }] | ONLINE };

Of course, you have this ability now on an installation-wide basis
with the available postmaster shutdown options.  It's difficult to get
excited about expending the work to make this doable on a per-database
basis, mainly because I foresee multi-database installations getting
much less popular once we implement SQL schemas.  Lots of schemas in
one (user) database per installation will become the norm, I think.
In that scenario a per-database shutdown option will be useless.
        regards, tom lane

> > But had to shutdown server first. So my question (and
> > suggestion) is to consider:
> > ALTER DATABASE <dbname> { OFFLINE [ { WAIT | IMMEDIATE }] | ONLINE };
> 
> Of course, you have this ability now on an installation-wide basis
> with the available postmaster shutdown options.  It's difficult to get
> excited about expending the work to make this doable on a per-database
> basis, mainly because I foresee multi-database installations getting
> much less popular once we implement SQL schemas.  Lots of schemas in
> one (user) database per installation will become the norm, I think.
> In that scenario a per-database shutdown option will be useless.

You can shut database access with pg_hba.conf.  I would edit
pg_hba.conf, shutdown postmaster to flush all pages, then start up with
database inactive.  You can then re-enable access to the database later
with pg_hba.conf.

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