brbackup -u / with password on rac

Hi expert:

Our system is netweaver 741 SP06 , db is oracle on RAC at ASM .

As note 914174 , we add the following parameters in /oracle/<SID>/sapprof/init<SID>.sap

_rem_sql_call = yes

_remote_exec = ssh

_remote_copy = scp

if the two instance is running ,  brbackup -u /       ,need enter password .

But when one instance is stopsed , brbackup -u / , don't need enter password, ther backup continue.

how to cancel enter password when brbackup -u / ?

Please give some advise how to solve the problem.

Thanks

Leo Lee