Problem while hiding password in script backup with Oracle RMAN

Hello,

I backup and restore OK for Oracle RAC with my script.

Now I need to hide password in backup script.

Current script ===================

if [ "$NB_ORA_FULL" = "1" ]
then
    BACKUP_TYPE="INCREMENTAL LEVEL=0"
    NB_SCHED="app-full"
elif [ "$NB_ORA_INCR" = "1" ]
then
    BACKUP_TYPE="INCREMENTAL LEVEL=1"
    NB_SCHED="app-diff"
elif [ "$NB_ORA_CINC" = "1" ]
then
    BACKUP_TYPE="INCREMENTAL LEVEL=1 CUMULATIVE"
    NB_SCHED="app-diff"
elif [ "$BACKUP_TYPE" = "" ]
then
    BACKUP_TYPE="INCREMENTAL LEVEL=0"
    NB_SCHED="app-full"
fi

.....

RUN {
ALLOCATE CHANNEL ch00   TYPE 'SBT_TAPE' PARMS='ENV=(NB_ORA_CLIENT=ora1-backup)' CONNECT='sys/oracle@oravn1';
ALLOCATE CHANNEL ch01   TYPE 'SBT_TAPE' PARMS='ENV=(NB_ORA_CLIENT=ora2-backup)' CONNECT='sys/oracle@oravn2';
SEND 'NB_ORA_SCHED=$SCHED_NAME,NB_ORA_POLICY=Backup-Oracle-oravn,NB_ORA_SERV=dr-backup-01';

BACKUP
    AS COMPRESSED BACKUPSET  
    $BACKUP_TYPE
    FORMAT 'bk_d%u_s%s_p%p_t%t'
    DATABASE;

release ch00;

release ch01;

}

===========================================

The Oracle Administrator suggest to pre allocate channel from RMAN;

CONFIGURE CHANNEL 1 DEVICE TYPE 'SBT_TAPE' CONNECT='sys/oracle@oravn1';
CONFIGURE CHANNEL 2 DEVICE TYPE 'SBT_TAPE' CONNECT='sys/oracle@oravn2';

But we cannot pass the value of $NB_ORA_SCHED to the channel. We need this parameter to configure SLP for each schedule.

===========================================

If we use Secure External Password Store, the Oracle Administrator worry that clients will need to change the method to connect to database. This database is in production and it make impact with such change.

===========================================

Is there a way to hide password in script ?