What does STRUCT RECORD Meaning for FTP?

I am trying to convert an existing FTP process that uses Korn Shell ftp
scripting over to Perl Net::FTP. I can easily get it working but in
the process I discovered something interesting. The current process
(Korn Shell script) uses the command "STRUCT RECORD". After talking
with the original programmer of this code, I was told that it was there
to preserve trailing spaces when doing an ascii transfer (MOST of our
files come from and MVS system). This is all fine and good but the code
uses STRUCT RECORD for ascii AND binary transfers. When it uses it for
binary transfers the number of bytes transferred is MUCH greater then
the actual number of bytes for the file and the transfer can take
almost twice as long as it does without using STRUCT RECORD. I have
searched the web and google and even looked at some RFC info but can
not find any statment as to what STRUCT REORD does.

I have this theory that is NOT necessary for binary transfers and in
fact considerably slows them done.

1) Does anybody know if my thery is correct.
2) Where can I find information as to what STRUCT RECORD does?

Thanks
Jim Locigno