Your network contains a System Center 2012 R2 Configuration Manager Service Pack 1 (SP1) environment. You discover that the last logon user details are not being updated for all of the client…

Active Directory User Discovery discovers user account objects in AD and populates user resource records, but it does not associate a user to a specific computer's last logon field.

Network Discovery identifies network infrastructure such as routers and subnets using SNMP and DHCP; it does not collect user logon information from client computers.

Heartbeat Discovery runs on the client itself and submits a DDR to the management point on a configurable schedule. This DDR contains properties including the last logon username, which updates the resource record in the Configuration Manager database. Because the information originates from the client agent at logon time, it is the most reliable method for keeping last logon user details accurate and up to date.

Active Directory System Discovery discovers computer objects in AD and can update general system properties, but it does not capture which user last logged on to a specific machine.