ORA-01017: invalid username/password; logon denied

[oracle@ashwani]$ sqlplus sys/oracle_4U@orcl as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Tue Apr 9 17:28:37 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

ERROR:
ORA-01017: invalid username/password; logon denied

Solution:
This might be the issue of permission of password file:

[oracle@ashwani]$ su -
Password:
-bash: i: command not found
[root@ashwani ~]#  chmod -R 777 /u01

[oracle@ashwani]$ sqlplus sys/oracle_4U@orcl as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Tue Apr 9 17:30:38 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Connected to:

Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select name, open_mode from v$database;

NAME      OPEN_MODE

--------- --------------------

ORCL      READ WRITE

Or
Create yhe local listener using netca utility.