Case 1:
SQL> show parameter REMOTE_LOGIN_PASSWORD
NAME TYPE VALUE
------------------------------------ --------------------------------- ------------------------------
remote_login_passwordfile string EXCLUSIVE
SQL>show parameter REMOTE_OS_AUTHENT
NAME TYPE VALUE
------------------------------------ --------------------------------- ------------------------------
remote_os_authent boolean FALSE
By default remote_login_passwordfile is EXCLUSIVE and remote_os_authent is FALSE. If you have something else here then make them EXCLUSIVE and FALSE which should resolve the problem.
SQL> alter system set REMOTE_LOGIN_PASSWORD= EXCLUSIVE
SQL> alter system set REMOTE_OS_AUTHENT = FALSE
Case 2:
I have such problem where I never explicitly set a password for the SYS user in the newly created database and I could still connect locally. I have fixed that by the following way:
1. Execute the following command in primary/target database.
SQL>ALTER USER SYS IDENTIFIED BY NEW_PASSWORD;
2. The command update the password file automatically $ORACLE_HOME/dbs/orapwORACLE_SID
3. Copy password file to standby server