Hello Devendra,
As you said , TR is still in main import phase since last 20 hrs. So it means Main Import is still running, RDDIMPDP job is use to trigger the tp only and it should finish with in couple of seconds. So means its fine.
Please check below points : -
1. go to /usr/sap/trans/log and check the Slog , Ulog and Alog.
2. go to /usr/sap/trans/tmp and check your Transport Number logs.
3. If the transport has big data then in the Transport log you will not find anything, but all the tp logs should be updated in tmp folder.
Please provide the tp log also specially for this transport.
Hope this is useful.
Regards
Pranay