Re: Why standby.max_connections must be higher than primary.max_connections?

On Tue, Dec 10, 2013 at 1:17 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> Because the KnownAssignedXIDs and lock tables on the standby need to
> be large enough to contain the largest snapshot and greatest number of
> AccessExclusiveLocks that could exist on the master at any given time.

Right. Initially during the development of Hot Standby, it looked like
the "max_connections >= master's" requirement on standbys wasn't going
to be necessary, or could be avoided. However, Simon gave up on that
idea on pragmatic grounds here:

http://www.postgresql.org/message-id/1252002165.2889.467.camel@ebony.2ndQuadrant

I'd thought about revisiting this myself, but I think that the impetus
to do so is lessened by recent work on logical replication.

-- 
Peter Geoghegan