Re: Point in Time Recovery

Simon Riggs wrote:
> On Fri, 2004-07-16 at 16:58, Zeugswetter Andreas SB SD wrote:
> > > >> Do we need a checkpoint after the archiving
> > > >> starts but before the backup begins?
> > > 
> > > > No.
> > > 
> > > Actually yes.
> > 
> > Sorry, I did incorrectly not connect 'archiving' with the backed up xlogs :-(
> > So yes, you need one checkpoint after archiving starts. Imho turning on xlog
> > archiving should issue such a checkpoint just to be sure. 
> > 
> 
> By agreement, archive_mode can only be turned on at postmaster startup,
> which means you always have a checkpoint - either because you shut it
> down cleanly, or you didn't and it recovers, then writes one.
> 
> There is always something to start the rollforward. 
> 
> So, non-issue.

I don't think so.  I can imagine many cases where you want to do a
nightly tar backup without turning archiving on/off or restarting the
postmaster.  In those cases, a manual checkpoint would have to be issued
before the backup begins.

Imagine a system that is up for a month, and they don't have enough
archive space to keep a months worth of WAL files.  They would probably
do nightly or weekend tar backups, and then discard the WAL archives.

What procedure would they use?  I assume they would copy all their old
WAL files to a save directory, issue a checkpoint, do a tar backup, then
they can delete the saved WAL files.  Is that correct?

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