Multiple WALs for PITR ?

I wan`t to use Point in Time Recovery
I allread read http://developer.postgresql.org/docs/postgres/backup-online.html#BACKUP-ARCHIVING-WAL

But I still wonder, if it is possible for PostgreSQL 8.0 to write multiple, redundant WAL-Files
like Oracles with its redo-log-groups ?

Is threre an equivalent to Oracles "ALTER SYSTEM SWITCH LOGFILE" ?

Thanks
Michael Kleiser