Sangiah's method can work but each rec has to have an id field so you can match the description to each rec that is read.
A better method is to include the following in the FD:
RECORD VARYING FROM x TO y DEPENDING ON WS-LEN
WS-LEN is defined in WS as PIC 9(5).
After each rec is read WS-Len will contain its length. If you want to write a V/VB rec make sure WS-LEN contains the desired len before issuing the WRITE. You can use the len from the READ if it's appropriate to your situation.