ORA-17629: Cannot connect to the remote database server when duplication primary db to standby via R

I am duplicating primary database to standby using the following ksh script:

rman target /  auxiliary  sys/pwd@PrimaryDBName<< EOF
RUN
{
ALLOCATE CHANNEL d1 TYPE DISK;
ALLOCATE CHANNEL d2 TYPE DISK;
ALLOCATE CHANNEL d3 TYPE DISK;
ALLOCATE CHANNEL d4 TYPE DISK;
ALLOCATE CHANNEL d5 TYPE DISK;
ALLOCATE CHANNEL d6 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv1 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv2 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv3 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv4 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv5 TYPE DISK;
ALLOCATE AUXILIARY CHANNEL cnv6 TYPE DISK;
DUPLICATE TARGET DATABASE
    FOR STANDBY
    FROM ACTIVE DATABASE
    DORECOVER
    SPFILE
  SET db_unique_name='StandbyDBName'