1. From transaction code SE16. Execute table USR02 in the field name. Execute again to display the list of the sap identical user in the system. You can find the user last logon date and time under TRDAT & LTIME columns. TRDAT = 00/00/0000, it means that the user never log on to the system since after the id creation date.
2. From SUIM. Go to By Logon Date and Password Change.
