Granted permission to oracle user scott..
grant sysbackup to scott;
SQL> select * from v$pwfile_users;
USERNAME SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS TRUE TRUE FALSE FALSE FALSE FALSE 0
SCOTT TRUE TRUE FALSE TRUE FALSE FALSE 0
sql>connect scott/tiger@orcl as sysbackup
Connected.
$>rman target scott/tiger@orcl as sysbackup
Recovery Manager: Release 12.1.0.2.0 - Production on Wed Mar 8 15:19:25 2017
Copyright (c) 1982, 2014, Oracle and/or its affiliates. All rights reserved.
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00554: initialization of internal recovery manager package failed
RMAN-04005: error from target database:
ORA-01017: invalid username/password; logon denied