Processing a very large database faster

I have a very large database on an AS\400 that needs frequent updating. The last time I appended data to this database, the RPGLE program took 19 days to run. After the initial program completed, I tried calling the RPGLE program from a CL program to see if I could speed up the processing speed. The CL program used Override Database File (OVRDBF) commands to read blocks of records using the Records Retrieved At Once parameter
(NBRRCDS(30000)). The Override Database File commands appear to not have made any significant difference. If you have any advice on how to speed up the processing speed of the program, I would be very grateful.