Rajendra,
We would not normally recommend trying to put one million assets on a mobile device. I would look at a filtering mechanism to reduce the number of records transmitted. I would probably also look to send pre-built clients out which are pre-loaded with the initial load of the data so that only deltas need to be sent on the first transmit.
Depending on what the 3rd part legacy system is capable of I would suggest considering directly linking to it from Agentry rather than pushing through ECC in temporary tables unless you cannot directly connect to it.
--Bill