ORA-01017: invalid username/password; logon denied

Try to connect to 12c standby database , then get “ORA-01017” error.

$ sqlplus sys/password@TESTDBSTY as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Tue Jan 15 18:07:54 2019

Copyright (c) 1982, 2014, Oracle. All rights reserved.

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

After investigation, found the listener is running by 11R2 binary, instead of 12cR1 binary.

Restart the listener in 12cR1 ORACLE_HOME, then everything is fine.

Always run listener by using the highest version of all ORACLE_HOME.