ORA-28017: The password file is in the legacy format.

SQL> alter user sys identified by iossKfGHsdsdUVu93xxswQ;
alter user sys identified by iossKfGHsdsdUVu93xxswQ
*
ERROR at line 1:
ORA-28017: The password file is in the legacy format.

Cause:

There are multiple possibilities for the cause of the error:

 * An attempt was made to grant SYSBACKUP, SYSDG or SYSKM.
 * These administrative privileges could not be granted unless the password file used a newer format ("12" or higher).
 * An attempt was made to grant a privilege to a user who has a large password hash which cannot be stored in the password file unless the password file uses a newer format ("12" or higher).
 * An attempt was made to grant or revoke a common administrative privilege in a CDB

Solution: 

Regenerate the password file in the newer format ("12" or higher).
Use the newer password file format ("12" or higher) if you need to grant a user the SYSBACKUP, SYSDG or SYSKM administrative privileges.

orapwd file=$ORACLE_HOME/dbs/orapwprod01 entries=5 force=y