ORA-28046: Password change for SYS disallowed

dbhost:dbname> alter user sys identified by "new_password";
alter user sys identified by "new_password"
*
ERROR at line 1:
ORA-28046: Password change for SYS disallowed



dbhost:dbname> show parameter remote

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
remote_dependencies_mode             string      TIMESTAMP
remote_listener                      string
remote_login_passwordfile            string      SHARED
remote_os_authent                    boolean     FALSE
remote_os_roles                      boolean     FALSE
result_cache_remote_expiration       integer     0

dbhost:dbname> alter system set REMOTE_LOGIN_PASSWORDFILE=exclusive scope=spfile;

System altered.

dbhost:dbname> shut immediate;

Database closed.
Database dismounted.
ORACLE instance shut down.
dbhost:dbname> startup;
ORACLE instance started.

Total System Global Area 2155233280 bytes
Fixed Size                  2161064 bytes
Variable Size            1442842200 bytes
Database Buffers          704643072 bytes
Redo Buffers                5586944 bytes
Database mounted.
Database opened.
dbhost:dbname> show parameter remote

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
remote_dependencies_mode             string      TIMESTAMP
remote_listener                      string
remote_login_passwordfile            string      EXCLUSIVE
remote_os_authent                    boolean     FALSE
remote_os_roles                      boolean     FALSE
result_cache_remote_expiration       integer     0
dbhost:dbname> alter user sys identified by "new_password";

User altered.