SAPDBA: Users and Roles 

You can display information about the current operating system and database users with the menu option User and Security.
The database user DB USER is the database user under which SAPDBA is logged on during a database session.

You are warned if the passwords which are set for the database users correspond to the standard values, so causing a loophole in security.

You can also display the roles of the standard users SYS , SYSTEM , OPS$ORAC11 and SAPR3 . The users SAPR3 and OPS$ORAC11 must not have a DBA role. SYS and SYSTEM must have the DBA role.

For more information about the user concept, see Users and Roles.