DUM DUM is a mix of many. I have attached a pic for better understanding.
From Down Side
1) 4 tracks come from SDAH main station-RED Line
2) 2 tracks come from KOLKATA station- GREEN Line
From...
more... UP Side
1) 4 tracks from NAIHATI side i.e. Belgharia side-RED Line
2) 2 Tracks from Chord Line i.e. Dakshineshwar Side-Orange Line
3) 2 tracks from Bangaon Side ie. Dum Dum Cant-BROWN Line.... from cantt stn one track goes to Biman Bandar (AIRPORT)