Switchover : WAL archiving and shutdown...

Hi,

I'm setting up switchover (to another server) with WAL/PITR.

But I'm wondering what is the behaviour of postgresql when you shut it down,
while a new WAL archive is just ready to be copied, or if the transfer
is in progress ?
Is it kept on hold, until the next start, or is it copied before leaving ?

In other words, when I want to switchover, is it sufficient to stop
postgresql,
and rsync the last partial WAL (the last modified one), or do I have to
check if
every WAL file is in sync before starting the other server ??

Thank you in advance,
Philippe Ferreira