INT 21 - Novell NetWare v3+ - ADD USER DISK SPACE RESTRICTION
        AX = F216h subfn 21h
        CX = length of request buffer in bytes
        DX = length of reply buffer in bytes
        DS:SI -> request buffer (see below)
        ES:DI -> reply buffer (ignored)
Return: AL = status
SeeAlso: AX=F216h/SF=24h

Format of request buffer:
Offset  Size    Description
 00h    WORD    000Ah (length of following data)
 02h    BYTE    21h (subfunction "Add User Disk Space Restriction")
 03h    BYTE    volume number
 04h    DWORD   (big-endian) object ID
 08h    DWORD   (big-endian) disk space limit in 4K blocks
                00000000h to 40000000h

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