If you want to reset the password of sys. you can recreate the password file with below cmd.
$ orapwd
Usage: orapwd file=<fname> password=<password> entries=<users> force=<y/n> nosysdba=<y/n>
where
file – name of password file (mand),
password – password for SYS (mand),
entries – maximum number of distinct DBA,
force – whether to overwrite existing file (opt),
nosysdba – whether to shut out the SYSDBA logon (opt for Database Vault only).
There are no spaces around the equal-to (=) character.
