Re: PITR WAL backups

Simon Riggs writes:
> >Mark Reidenbach wrote
>
> >The problem I'm having is that you need to
> > backup this wal
> > file before it's been archived to have a backup which is
> > consistent
>
> Not sure I agree. Can you explain some more?
>
> Is it that you have a very low transaction rate and log files take a
> long time to fill?
>
Independently from the transaction rate it's not clear to me, at which
point (that is after saving which WAL) an online backup will be safe
to be usable.
I start the backup, save the files, end the backup. Ok.
Now there are transactions during the backup. They are written to WALs.
Some of these WALs are archived but the last transaction might be stored
in WALs that are not archived yet, when the backup ends.

So when can I be sure, to have all transactions that occured during the
backup in archived WALs?
Do I just have to wait that there is one further WAL archived after
the backup?

If that's the case, then online backups at low transaction rates might
take some time. I guess one can live with that. If you keep the previous
backup and the WALs so far, you can still recover from that, while waiting
for the current backup to become safe.

But the documentation it didn't make clear to me, at which point I can
rely on the backup.

Morus