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From: Shinya Kato <shinya11.kato@gmail.com>
Date: Thu, 5 Feb 2026 15:47:04 +0900
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Subject: Re: Placement of synchronized_standby_slots description in
 config.sgml
To: Fujii Masao <masao.fujii@gmail.com>
Cc: pgsql-docs@lists.postgresql.org
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On Fri, Jan 23, 2026 at 7:22=E2=80=AFPM Fujii Masao <masao.fujii@gmail.com>=
 wrote:
>
> Hi,
>
> synchronized_standby_slots is defined in guc_parameter.dat as part of
> the REPLICATION_PRIMARY group and appears under the "Primary Server"
> section in postgresql.conf.sample. However, in the documentation
> its description is placed under the "Sending Servers" section.
>
> Given this, it seems the description should also be under "Primary Server=
"
> in the documentation. I've attached a patch that moves it there.

Thank you for the patch! The patch LGTM.

> Alternatively, if synchronized_standby_slots is intended to be set also
> on a standby in cascading replication setups, then the current documentat=
ion
> placement may be correct, and instead guc_parameter.dat and
> postgresql.conf.sample should be updated. My understanding, though,
> is that this parameter is normally set only on the primary. Right?

You're right. PhysicalWakeupLogicalWalSnd() in walsender.c has this check:

    /*
     * If we are running in a standby, there is no need to wake up walsende=
rs.
     * This is because we do not support syncing slots to cascading standby=
s,
     * so, there are no walsenders waiting for standbys to catch up.
     */
    if (RecoveryInProgress())
        return;

So this parameter is only meaningful on the primary.

--=20
Best regards,
Shinya Kato
NTT OSS Center