>>>>>

>>>            IF InternetWriteFile (hTarget, @lcBuffer, lnLength, @lnLength) = 1
>>>                lnBytesWritten = lnBytesWritten + lnLength
>>>                Wait Window NoWait "Processing . . ."
>>>>>

>...
>>>the records are still truncated at 256
>>>Record Length is truly 320
>When I debug lnLength is showing 320 multiple
> but MainFrame Programmers are getting 256.
>
>>What command do you send to mainframe to set record size? Did you check for errors after that command execution?
>
>No other commands (like Set Record Size) that I'm aware of ...
>
>? lcbuffer && shows complete 12 records as expected

How would mainframe know that you want recordsize 320 bytes for this file?