It looks to me like this isn't a true variable length field we're dealing with. So, in that case, simply define a DDS file with a single field in it, and concatenate the hex character as you go along.
For example (using hex 'FF' as the delimiter):
Record = Field1;
Record = %trim(record) + x'FF' + Field2;
...
Record = %trim(record) + x'FF' + Fieldx;
Write RecName;
In V5R3, the maximum length of a string (and, therefore, your record) is 65535 bytes.
-- Francis
I'd like to change the world, but I can't find the source code.