Whatsapp on dual sim I want to use dual sim phone with one number registered with whatsapp and another number with data pack , is it possible?
Short answer
No, because WhatsApp doesn't officially support multiple accounts.
Longer Answer
It's technically possible, but you'll need two different versions of WhatsApp. Customised ('modded') versions of WhatsApp exist, and if you install both the official version and a reliable unofficial version, you can in fact have two WhatsApp numbers on the same phone.
However, you shouldn't do this if you're concerned about privacy because the unofficial versions of WhatsApp aren't vetted by any authority and might compromise your device.
Furthermore, there always remains a possibility the unofficial version will simply stop working, because WhatsApp doesn't like them and has begun cracking down on them. There are even (unsubstantiated, and later refuted) rumours that WhatsApp will permanently ban users of unofficial clients.
Instead of installing an unofficial version, you can edit the build.prop file to make it appear as if two copies of WhatsApp are completely different applications but you will definitely run into issues later on as both will try to save messages and media to the /sdcard/WhatsApp folder, resulting in conflicts and confusion.