Hello Mohit
SDM is a feature that manages CAM and TCAM on a physical device. It doesn’t actually change the way a device will operate. Virtual devices on GNS3 don’t have CAM and TCAM, so there is nothing to manage. Remember GNS3 is an emulator, which means it runs real IOS operating systems on your computer hardware. The computer hardware doesn’t have CAM and TCAM, so the feature itself cannot function.
In order to see these features in action you will have to either use a simulator like Packet Tracer, which simulates the existence of these memory types and responds appropriately, (but only to a certain extent as you can see) or you must use real hardware.
Most L3 switches have this feature including the 3750, as well as the higher 4500/4600/9400 and 6500/6600/9600 series catalyst chassis switches.
You can find out more about SDM and GNS3 at this GNS3 forum thread.
I hope this has been helpful!
Laz