Hi,
You can check the tables in 'extended process monitor', select the 'Task icon (arrow icon)' for the latest execution number. There you see the subactivities which are in 'running' status. You click on the running subactivities, there you can find the migration object names which are in running status for data selection.
Alternatively, you can go to transaction DTLMON in the central system, give the mass transfer id.
To get the mass transfer id, check the log of activity "Definition of mass transfer id for participating tables".
In DTLMON, you need to go to "Relevant tables" tab and see the tables which are in "In process" and "Not calculated" status.
Hope it helps.
Thanks,
Rupam