Is it required to connect to the ServiceDesk MDB Database using a Oracle SYS user while configuring ServiceDesk?
No, it is not mandatory to connect with a SYS user. All that is required is an Oracle user with DBA and SYSDBA Roles (administrator privileges) so that the mdbadmin account (application user) can be created/granted with access to various system tables. It not necessarily be SYS or SYSDBA.
The steps mentioned in the CA SDM Implementation Guide -> Plan the CA MDB Installation -> CA MDB Considerations provides the steps to create another user instead of SYS. The example mentioned for each step, the "installation_user" is the one being granted the required privileges and will be used in during the CA SDM configuration.