could anyone tell me how to switch the location of archive log file without shutdown db?

init.ora

log_archive_dest = /ora/arch1/@/arch.log
log_archive_duplex_dest = /ora/arch2/@/arch.log

I know I can issue:

alter system archive log stop;
alter system archive log start to 'new location';

but it only change the first one, how about the duplex dest?

thnaks in advance