--Tempdb session File usage 
--sys.dm_db_session_space_usage : Returns the number of pages allocated and deallocated by each session for the database.
--sys.dm_exec_sessions: Gives details about the sessions.

SELECT
                    sys.dm_exec_sessions.session_id AS [SESSION ID],
                    db_name(sys.dm_db_session_space_usage.database_id) AS [DATABASE Name],
                    HOST_NAME AS [System Name],
                    program_name AS [Program Name],
                    login_name AS [USER Name],
                    status,
                    cpu_time AS [CPU TIME (in milisec)],
                    total_scheduled_time AS [Total Scheduled TIME (in milisec)],
                    total_elapsed_time AS    [Elapsed TIME (in milisec)],
                    (memory_usage * 8)      AS [Memory USAGE (in KB)],
                    (user_objects_alloc_page_count * 8) AS [SPACE Allocated FOR USER Objects (in KB)],
                    (user_objects_dealloc_page_count * 8) AS [SPACE Deallocated FOR USER Objects (in KB)],
                    (internal_objects_alloc_page_count * 8) AS [SPACE Allocated FOR Internal Objects (in KB)],
                    (internal_objects_dealloc_page_count * 8) AS [SPACE Deallocated FOR Internal Objects (in KB)],
                    CASE is_user_process
                                         WHEN 1      THEN 'user session'
                                         WHEN 0      THEN 'system session'
                    END         AS [SESSION Type], row_count AS [ROW COUNT]
FROM sys.dm_db_session_space_usage
                                         INNER join
                    sys.dm_exec_sessions
                                         ON sys.dm_db_session_space_usage.session_id = sys.dm_exec_sessions.session_id