Message-ID: <cce9a45811c96b38bf1774e41a6cf5877386b554.camel@cybertec.at>
Subject: Re: Activate a standby database and then revert to standby
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Massimo Ortensi <mortensi@unimaticaspa.it>,
	pgsql-admin@lists.postgresql.org
Date: Thu, 28 Oct 2021 11:41:07 +0200
In-Reply-To: <1mg1SF-000Mdb-9e@unimaticaspa.it>
References: <1mg1SF-000Mdb-9e@unimaticaspa.it>
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On Thu, 2021-10-28 at 11:12 +0200, Massimo Ortensi wrote:
> I need to activate (open in read and write) a standby database, perform 
> some action and then revert it to the previous status of standby and 
> thus starting again loading wals from when it stopped.
> 
> How should I proceed to be sure it's possible to get "back in time" to 
> the standby db ?
> It's a huge DB and can't afford restarting sync from scratch

Yes.  For that, you have to enable "wal_log_hints" and set "wal_keep_size"
high enough.  Then you can use "pg_rewind" to restore the promoted standby
to a state when it can be a standby again.

Yours,
Laurenz Albe
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