PA7280@UTKVM1.BITNET ("Benjy Alford 974-6721", 615) (09/13/89)
Our current network standard says that ASCII tubes should be set for 7 bit Even parity. The VAX & TCP/IP folks are pushing for a policy/standards change to 8 bit none for ASCII tubes on our campus. We are running VM/XA SF2, VM/HPO 5.0 and MVS/XA 2.2 supporting 3270-type access via 7171's and line-mode access via 37x5 EP. I understand how to change the 7171's from 7 Even to 8 None, but what implications are there for the line-mode access? Any pilgrams already done this? Any drawbacks? Benjy Alford University of Tennessee, Knoxville
jcmorris@mbunix.mitre.org (Joseph C. Morris) (09/14/89)
In a recent article Benjy Alford <PA7280%UTKVM1.bitnet> writes: > I understand how to >change the 7171's from 7 Even to 8 None, but what implications are there >for the line-mode access? Any pilgrams already done this? Any drawbacks? As far as VM is concerned, none. Unless there's a strange dependency in VM/XA, it couldn't care less about the parity bit on inbound data, and unless locally modified will generate mark parity on transmitted data. When I was at Tennessee I modified the VM code to emit even parity to be consistent with the Series/1 requirements; if you want to have it emit space parity the translate tables are now in DMKTBN, although there are several other places like DMKTTY where there are hard-coded ASCII strings which will need to be fixed up. I don't have the faintest idea where MVS now keeps its translate tables. They are probably buried in the middle of VTAM for 270x emulated lines, and will be in the 37x5 NCP code for lines handled there if you are thinking about adding them later. Generally, the IBM systems are insensitive to inbound parity, although there are always some strange cases like the 3708. What may bite you is if you don't (or can't) make the IBM systems emit 7/space (which is a special case of 8/none) then you will have problems with terminals which cannot be set to 7/anything/ignore-parity-errors. VT220 terminals, for example, have the ability to specify a parity for transmited characters while ignoring the parity it receives. TELNET interfaces, on the other hand, usually don't have any mode other than 8/none and display gibberish on the screen when connected to a system running 7/even, odd, or mark. (Remind Jim Grossen of the hardware mod he had to do on the LA120 to make it ignore parity.) Looking back at the above paragraph, my memory is coming up with a vague recollection of having to patch TCAM (IEDQ21??) for some parity question, but I'm not sure if it involved the handling of received characters or just transmitted ones. In any case, anyone still using TCAM deserves problems. I've never worked on VTAM under MVS. (Mystery of the ages: why won't IBM allow users to set their terminal characteristics as easily as DEC does with VMS?) You also need to make sure that any network interfaces are running with 7/space if all your terminals require it. I would hope that the DCA system is set up that way... Good luck.