ORA-01017 when connecting remotely as sysdba
Filenames (and Oracle instance names) on Linux are case sensitive. You keep using MYSID but you created the password file as orapwmysid. MYSID as a TNS alias is not case sensitive. MYSID as an instance name is case sensitive and having the password file named lowercase will prevent logging in using SYS with the above error.

[oracle@o71 ~]$ ps -ef | grep smon
oracle     923 31725  0 16:56 pts/0    00:00:00 grep --color=auto smon
oracle   31761     1  0 May15 ?        00:00:37 ora_smon_MIN18
oracle   32529     1  0 16:49 ?        00:00:00 ora_smon_MIN19
[oracle@o71 ~]$ ls -l $ORACLE_HOME/dbs/orapwMIN19
-rw-r-----. 1 oracle oinstall 2048 Apr 30 00:17 /u01/app/oracle/product/19.0.0/dbhome_1/dbs/orapwMIN19
[oracle@o71 ~]$ sqlplus sys/Oracle123@min19 as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Wed May 29 16:56:37 2019
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL&gt; exit
Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
[oracle@o71 ~]$ mv /u01/app/oracle/product/19.0.0/dbhome_1/dbs/orapwMIN19 /u01/app/oracle/product/19.0.0/dbhome_1/dbs/orapwmin19
[oracle@o71 ~]$ sqlplus sys/Oracle123@min19 as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Wed May 29 16:56:45 2019
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.

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


Enter user-name:


Even if you change the SYS password with ALTER USER..., the password file will not be generated correctly in this case:

[oracle@o71 ~]$ sqlplus / as sysdba

SQL*Plus: Release 19.0.0.0.0 - Production on Wed May 29 16:58:19 2019
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.


Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0

SQL&gt; alter user sys identified by Oracle123;

User altered.

SQL&gt; Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
[oracle@o71 ~]$ ls -l /u01/app/oracle/product/19.0.0/dbhome_1/dbs/orapw*
-rw-r-----. 1 oracle oinstall 2048 Apr 30 00:17 /u01/app/oracle/product/19.0.0/dbhome_1/dbs/orapwmin19
[oracle@o71 ~]$