Re: Standby server won't start

From: "Tatsuo Ishii" <ishii@postgresql.org>
> Last time I tested in following way, max_connections in pg_control of
> standby did not reflect the change in primary.
>
> 1) stop primary
> 2) stop standby
> 3) change max_connections to 4 in primary
> 4) change max_connections to 4 in standby
> 5) start primary
> 6) start standby but it failed as I said before
>
> So the particular WAL record was not sent to standby?
> I'm going to test again...

That's because the parameter is checked at the beginning of recovery (i.e. 
at standby start) before XLOG_PARAMETER_CHANGE is received and applied on 
the standby.  Please see CheckRequiredParameterValues() in StartupXLOG().

To persist the max_connections change:

1) stop primary
2) change max_connections on the primary
3) start primary
4) watch pg_stat_replication to wait until the standby is sync with the 
primary (XLOG_PARAMETER_CHANGE is applied)
5) stop standby
6) change max_connections on the standby
7) start standby

Regards
MauMau