Hi Sumit,
The R/3 System has a default superuser, SAP*, in the clients 000 and 001. A user master record is defined for SAP* when the system is installed. However, SAP* is programmed in the system and does not require a user master record.
If you delete the SAP* user master record and log on again as SAP* with initial password PASS, then SAP* has the following attributes:
1) The user is not subject to authorization checks and therefore has all authorizations.
2) The user has the password "PASS", which cannot be changed.
Please also refer SAP Notes 2383 and 68048 for more information.
BR,
Kaivalya