#!/bin/cat
$Id: FAQ.TTL.txt,v 1.1 2017/05/03 22:27:45 gilles Exp gilles $

This documentation is also at http://imapsync.lamiral.info/#doc

=====================================================================
   Imapsync tips about TTL when changing name resolution of hosts
=====================================================================

Why decrease the TTL (Time To Live) delay in DNS configuration, down
to 5 minutes?

A small TTL is not mandatory, it's safer and more easy to work with when
migrating.

It's about how long it takes to be sure the users are using the new
imap host, and how long it takes to be sure all new incoming messages
are going right now at the right place. Will you shut down the old
server just after the resolution change? I guess you won't and you'll
be right.

The TTL is just a value, very well supported by machines, with a
little name resolution supplementary work for them when it is set to a
small value like 5 minutes, but it's a tremendous comfort for migrator
people like us.

Be sure to wait 24h after this TTL change before changing any
resolution since the TTL change has to be propagated as well. After
the migration done, no problem to set back the TTL to 24h or more. If
you can't decrease TTL under 4h or even 24h, it's ok anyway, imapsync
can sync the new messages dropped in the old server.