The following message is a courtesy copy of an article that has been posted to bit.listserv.ibm-main,alt.folklore.computers as well.
[EMAIL PROTECTED] (Michael Knigge) writes: > I wonder how it is possible to attach DASD- or TAPE-Devives via > TCP/IP. There is a product called mfnetdisk (see mknetdisk.com) that > is able to "emulate" a 3390 that resides on a PC and is accessed via > TCP/IP. > > So... I ask myself how this is possible. And (for me) even more > interesting, would it also be possible to do the same for a Tape? for historical reference ... the internal "csc/vm" vm370 release ... mentioned in this old email http://www.garlic.com/~lynn/2006v.html#email731212 http://www.garlic.com/~lynn/2006w.html#email750102 http://www.garlic.com/~lynn/2006w.html#email750430 was somehow leaked to at&t longlines circa 1975. they took this highly modified "csc/vm" vm370 release and made numerous local modifications ... including remote device support ... that would run over various kinds of communication links. basically virtual machine channel program simulation would forward the stuff to remote site for actual execution on the real locally attached device. this system manage to propogate to a number of at&t longline machines. Nearly a decade later, the at&t national account manager managed to track me down ... longlines had continued to migrate the vm370 system thru various generations of mainframes ... but it came to an end with move to 370/XA ... and he was looking for assistance in helping move longlines off that vm370 system. this isn't all that much difference with standard i/o virtualization, aka a copy of the "virtual" channel programs are replicated with real address substituted for virtual addresses. in the case of remote device, the replicated "real" channel programs are run on remote system ... with appropriate fiddling of virtual pages on the application machine and the real pages on the machine where the device was attached. some amount of the fiddling was handled by services running in a separate virtual machine. note this isn't all that different from what is done by various virtual machine mainframe simulators that run on various other kinds of platforms ... and include simulation of various kinds of mainframe i/o devices on completely different kinds of devices. the specific communication mechanism used is the least of the issues. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
