Using the B data type in files

We have a file that is used by all of our clients, and it's a high volume transaction table of sorts (adding 1 byte to the file equates to roughly 190mb of storage, assuming 200 million records total, and if I'm doing my math right: 200,000,000 /1024 /1024). Because of this, and disk space, there is resistance to adding new fields to the file. We have additional disk budgeted, but who knows if that will get approved.

I have approval to add 5 identifier columns. I was going to add them as 9p 0 (5 bytes) each. However, I could get the same values for less space if I used the B data type (9b 0), saving almost 1gb in storage.

In my 10+ years of RPG programming, I've never dealt with a B type on a file (in fact, only ever in IBM supplied APIs, and even then I converted them to integer types).

I did find that there is a EXTBININT header spec, but I don't really see the purpose to using it (I mean I know you can then access the 10th digit, in the case of 9b 0, but does that 10th digit get stored on the file?

Are there any gotchas to using the B data type?

Thanks,
Kurt Anderson
Sr. Programmer/Analyst
CustomCall Data Systems, a division of Enghouse Ltd.