INT 21 - Novell NetWare - WORKSTATION - SET NetWare ERROR MODE
AH = DDh
DL = error mode
00h invoke INT 24 on critical I/O errors (default)
01h return NetWare extended error code in AL
02h return error code in AL, mapped to standard DOS error codes
Return: AL = previous error mode
Note:   this function is supported by Advanced NetWare 2.0+

See also: 24

21DD - Novell NetWare - WORKSTATION - SET NetWare ERROR MODE