Data size from each polling engine

Honestly it would be quite a massive undertaking to get that and have it be truly accurate.  You'd basically be needing to join almost every table in the database back to the engines table and sum up the byte count for each row.  There are hundreds of tables depending on which modules you have. 

Ultimately I am hard pressed to understand exactly what the goal you would be looking to accomplish here is?  If you are looking to do some kind of relative database cost analysis you'd probably have a much easier time ball parking it based on element/component count as a percent of total polled objects.  Something like APE2 has 20% of the total elements, so we will say it roughly represents 20% of overall database size. 

Purpose of asking this data is we are having one change during which ape nd management server nd database connectivity will be lost. As per SW recommendation,ape can polled the devices and store 1gb or 1hr of data, after that data will be discarded.Once the connection restored data xfered to database.

We want to know in 1hr ape can polled how much of data size??

The 1 hour of data is actually incorrect, the apes will stash data in msmq storage until the drive fills.  It's a common complaint for people to have cases where they have intermittent issues that cause their ape to fill the drive completely. Once db service is restored you can stop/restart the Orion and msmq services and it will shoot the cached data into your db.

Appox data is also fine. Is there any way i can find out approximate polling data gatehered by APE in 1 hour depending on the number of devices APE is monitoring?

Add a firewall rule to your db server blocking that ape for 15 min and see how much data ends up in the msmq storage folder and project that out?

If you have NTA and a layer 3 device in the network path you could try to measure the conversations between the ape and database server for an hour.

Run wireshark or another packet capture tool on the ape to measure traffic going out to the db.

Thank you.