Online backups and WAL

Hi,

I'm currently testing online backups, and I'm facing the problem of a missing
WAL when I do the backup : the current WAL isn't archived when I save the
archives, and is required to recover...
I've read in the mailing list archives that it can be solved by copying the
current WAL from pg_xlog. Even if this solution works, it looks to me to be
more of a workaround than anything else, and adds some complexity to an
operation that is allready not that simple.
I'd like to know if there is a way to force the switch from a WAL to the next
one, like with an 'alter system archive log current' in Oracle.

Cheers.

Marc Cousin