Re: Point in Time Recovery

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Point in Time Recovery
Date: 2004-07-16 15:25:56
Message-ID: 46C15C39FEB2C44BA555E356FBCD6FA40184D155@m0114.s-mxs.net
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> then on restore once all the files are restored move the
> pg_control.backup to its original name. That gives us the checkpoint
> wal/offset but how do we get the start/stop information. Is that not
> required?

The checkpoint wal/offset is in pg_control, that is sufficient start
information. The stop info is only necessary as a safeguard.

> Do we need a checkpoint after the archiving
> starts but before the backup begins?

No.

> Also, when you are in recovery mode, how do you get out of recovery
> mode, meaning if you have a power failure, how do you prevent the system
> from doing another recovery? Do you remove the recovery.conf file?

pg_control could be updated during rollforward (only if that actually
does a checkpoint). So if pg_control is also the recovery start info, then
we can continue from there if we have a power failure.
For the first release it would imho also be ok to simply start over if
you loose power.

I think the filename 'recovery.conf' is misleading, since it is not a
static configuration file, but a command file for one recovery.
How about 'recovery.command' then 'recovery.inprogress', and on recovery
completion it should be renamed to 'recovery.done'

Andreas

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