We can use control table update and ipf files for capturing incremental data or delta data from a source. Control table will maintain the details like from which timestamp (previous) to which timestamp (current) we have taken the data.
If the session is taking data everyday (daily run) then the delta will be of one day. Previous timestamp will be of yesterday's date (P1) and current timestamp will be the time (C1)of run of the job. So in today’s run we will get one day data.
Next day when job runs C1 will become P2 and today’s run time will become C2, so we will not miss any records incremented i the source systems. This will go on.
Incase on weekly runs the delta will be of one week.
Let me know if you need any further information.