Hi @NagarjunaS16644648: Can you please explain more on the issue. Generally you will have Data Transform available as source for both List and page type of Data pages.

See more details here under section Data Source.

Thanks.

@NagarjunaS16644648  data page is reffered to as Live data in pega terms and that means it can get data data from anywhere/any source and make that data available to any system.

Sources-> data transform, activity, connect-rest, robotic process automation etc. 

From the sources you can see, 

You can get data from external system or from internal DB(pega) and copy/transfer it to pega using any the above sources. 

You can use appendto, appendandmapto in DT for data manipulation, in activity also we can do data manipulation, we can get data from external api using connect rest and map into pega, we can use robotic process automation to act on top of external application and get data.