Harold,
I
think I turned attachments off. Just create a temp folder in
the files section and upload, then only those who need it
download it.
Dave
?
?
Thanks so much for your responses.
My first question, can the VM's memory contents be
"extracted" from the virtual machine and this content be moved
from the VM system for processing is in fact possible.? Is it
worth doing?? It is clear if I were to go in that direction,
it would be a separate utility.
As is frequent with such questions, the concept got expanded
somewhat.? Happy to see it stimulated a few "grey/gray cells".
?
I appreciate the suggestion of how to do this with a VM
system.? However, I do not have a running VM system.? I gave
up all personal interest in system administration of all sorts
by the time I retired.? If someone is willing to produce such
a dump in a form my Linux PC could read, I would appreciate
it.? If not I understand that too.? It would give me an idea
of whether this separate utility might be worth looking at
developing.
Just a little background:
I have been working on a bare-metal development system (SATK)
used outside of a mainframe.? My frustrations working on
OpenSolaris support in Hercules drove me to realizing this
tool would be of value.? A lot of Hercules tests now use
SATK.? My work with QEMU finally drove me to work on closing
the loop by producing a memory dump for this development
system.
This is unlike your usual experience where everything is
developed within VM (CMS), run on VM, and the output examined
on VM.? In the SATK environment the bare-metal program is
build outside the mainframe, loaded into it, and the output's
destination, in this case a dump, is also outside the
mainframe, the PC.
Again, thanks so much.? I have a fully working version for
the S/370 world.? Does anyone know if this list supports
attachments?
Harold Grovesteen
On 3/27/24 04:07, Frank D. Engel, Jr.
wrote:
Wondering if the proposed new command could actually be
added at the CP level instead of the CMS/MVS level.
CP might save the state of the machine to a prepared
location in DASD then restore it when the user next logs in,
essentially mimicking the VMWare (for example)
suspend/restore capability.? Users can already disconnect
and leave the machine intact to reconnect to it later (even
leaving it running in the background), so from a user
perspective this would extend that with the option to
reconnect to it even after a shutdown / re-ipl of VM, but
without leaving it running in between.
There would obviously be limits to this when working with
dedicated hardware, but for virtualized hardware as with a
typical CMS machine, I would think it could be done (granted
with a fair amount of effort)?
?
On 3/27/24 00:23, Bertram Moshier
wrote:
Hello Harold,
What you desire doesn't exist in
VM/370 today, but it is possible.? Cray Supercomputers
are real memory systems that use swapping to allow
multiple users to use the same real memory space.? IBM
went with paging for its solution to this problem.?
Seymore Cray rejected this method because it added
around seven cycles?to each operation
referencing?memory.
Let us see if I understand you
correctly.? You want to take a snapshot of a virtual
machine's memory (e.g., 0 to maximum storage size of
the machine).? How you accomplish this depends upon
what you want to do with the image and the memory
methodology used by the users' virtual machine
operating system.
There are two methods for
collecting a copy of the memory for offline
examination.? They are:
1) Copy the state of the virtual
machine to a binary file.? What we used for the Cray
IBM VM Station. When an error occurred, the station
would dump all of its memory, registers, etc., to a
file. We had tools to examine the station and even
run it to the point of failure. (We would use the
internal trace to simulate the interrupts and data
transmissions (to and from the Cray and users'
virtual machines).) This improved the station's
stability?so we could catch coding and design issues
before shipping the product to customers.
2)? You could (as Bob suggested)
use the existing CP DUMP command.? A better solution
would be to allow CP to dump the data more than the
printer.
On the other hand, if you want to
stop and restart an operating system without regard to
space or time and support both paging and swapping,
you will need to add a new command to the operating
system. This would be similar to Windows hibernation
but with more functionality.? As this new command is
at the operating system level (e.g., MVS), it would
support both real and virtual environments.
?
?
For my
Stand Alone Tool Kit project I am working on the
ability to
create a formatted memory dump.? It depends upon
preserving the
machine's memory in a host (Windows, Linux, etc.)
platform's host file
system.? With Hercules this is accomplished using the
Hercules command
'savecore'.
SATK is sometimes used with z/VM virtual machines.?
So, I am asking:
is it possible to transfer the contents of a virtual
machine's physical
(absolute storage) memory out of VM (any version,
VM/370 or z/VM) in any
manner at all?
The assumption is that a bare-metal program has been
executing within
the virtual machine, so CMS is out of the picture.?
This would strictly
be CP commands as I understand things.
Assuming the storage contents exists outside of the
virtual machine,
whatever format that turns out to be, can be
manipulated for use by the
dump program.? Separate problem for later.
Note, I am not opposed to a programmatic approach from
within the
virtual machine embedded within the bare-metal program
if required to
get the memory content out of the virtual machine, BUT
only if that is
the only way.
Asking the experts...
Harold Grovesteen
