how to correct TRFC and ARFC related errors

Dear friends,

When we are pulling data from R3 in to BW. some datasources are terminating with timeout error...

And for the same if we check in R3 -- sm50 it is still displaying that the <b>processing Background Workprocess is in HOLD status and reason is ARFC</b>

we are unable to approach this problem..... what to check and how to correct these kind of errors.

Thank u.