Hi Rajesh,
I order to use live data there are various conections available in Dashbords.
Qaaws
Live office
Query browser
SAP BW
You could go through the user guide for detailed information on the same based on your requirement .
Following is the link for Dashboards user guide.
http://help.sap.com/businessobject/product_guides/boexir4/en/xi4_dashD_user_en.pdf
Hope this helps .
Regards,
Noopur