Steve Myers wrote:
The problem is EXCP access to the VTOC. There are a lot of programs
that do that.
so there is a conversion period with some trailing support for old
disks for extended period of time ... which would have been pretty
much over if started in back in the early 80s.
also, could provide software simulation for CKD channel programs that
refuse to die ... basically as side-effect of virtual-to-real channel
program translation ... by whatever descendent of CP67's CCWTRANS
currently running in MVS. recent posts about initial mvt->VS2 converstion
was done by hacking CP67's CCWTRANS into the side of the MVT kernel
http://www.garlic.com/~lynn/2007e.html#27 IBM S/360 series operating systems
history
For virtual machine support, CP67's CCWTRANS had to copy the virtual
machine's channel program to a "shadow" channel program that reference
real addresses. The same thing applies to channel programs from the
applications virtual address space (that is loaded with virtual
addresses) that need a real version of the original (virtual) channel
program created for "real" execution.
While the original CP67 CCWTRANS somewhat did (nearly) a one-for-one
conversion of each virtual CCW to a shadow/real CCW ... there were
various enhancements over the years (by both internal accounts and
customer accounts) that implemented full software simulation for
special/custom devices. Such implementations could be similarly moved
into the MVS kernel in a manner similarly to the way that CP67's
CCWTRANS was initially moved into VS2.
The strict exception to the above are any system applications that
run channel programs in "virtual equal real" where the requirement
for translation & shadow channel programs are eliminated ... however,
these should be a much smaller enumerated set of applications
that would be in need of converstion.
Another example of such body of work is the various emulators that
allow current generation 360-genre operating systems and various other
processor architectures ... like intel and other machines. These
include similar capability to the original CP67 channel program
translation ... and I believe most of them also implement CKD
emulation on fixed-block real devices. In manner similar to migration
of CP67's CCWTRAN channel program translator into VS2 kernel
... perform somewhat analogous migration of various software CKD
channel program emulation into the MVS kernel.
The other body of code providing similar function is all the hardware
controller functions emulating CKD operations on devices that are
really fixed-block architecture of one form or another. Provide
some flavor of this as part of conversion transition.
one of my early contentions that it would have been much simpler and
easier and have much longer term benefits than the iteration
involving adding support for ECKD. The need for any of the ECKD-type
stuff would have mostly evaporated in transition of CKD to fixed-block
architecture environment
post posts in this and related thread:
http://www.garlic.com/~lynn/2007d.html#48 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007d.html#51 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007d.html#65 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007d.html#69 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007d.html#72 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007e.html#27 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007e.html#33 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007e.html#35 FBA rant
http://www.garlic.com/~lynn/2007e.html#38 FBA rant
http://www.garlic.com/~lynn/2007e.html#39 FBA rant
http://www.garlic.com/~lynn/2007e.html#40 FBA rant
http://www.garlic.com/~lynn/2007e.html#41 IBM S/360 series operating systems
history
http://www.garlic.com/~lynn/2007e.html#42 FBA rant
http://www.garlic.com/~lynn/2007e.html#43 FBA rant
----------------------------------------------------------------------
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
