I can see how VM, itself, can talk to Hercule via Diag 8, but how would a guest OS or CMS program?? Wouldn't a Diag 8 in a virtual machine go to VM as a CP command instead of to Hercules.?
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You're correct it might be a security risk, but maybe it should be an option and up to the system's owner.
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Thank you.
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On Sat, Nov 19, 2022, 11:21 Joe Monk <joemonk64@...> wrote:
"I'm wondering if it is possible for a VM machine / CMS program to have Hercules change tapes?"
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DIAG8CMD ??DISABLE?| ENABLE ? [ECHO |?NOECHO]
When?ENABLE?is specified the Hercules Diagnose 8 instruction command interface is enabled, allowing the guest to directly issue Hercules commands via the Diagnose 8 instruction. When set to?DISABLE?all Diagnose 8 instructions cause a Specification Exception program interrupt to occur instead.
An optional second argument can be given to request whether an audit trail of such commands should be created or not. When?ECHO?is specified, a message is issued when the command is about to be issued, when the command is redisplayed (as is normally done when entered from the command line), as well as a final message indicating the command has finished executing. When?NOECHO?is specified no such audit trail messages are displayed and the command instead completes silently (except for whatever messages the command itself may issue).
Security Alert:??Enabling this feature has security consequences. When this feature is enabled it is possible for guest operating systems running under Hercules to issue commands directly to the host operating system by means of the?sh?(host shell command) and?exec?(execute Rexx script) commands. This ability may be disabled via the??statement's?NODIAG8?option.
The value of?ECHO?or?NOECHO?has no effect on whether or not command output will be placed into the Diagnose 8 instruction's response buffer if the instruction requested one, nor does it cause the resulting audit trail messages from being placed into the response buffer either. The?ECHO?option only impacts what is displayed on the hardware console (and what appears in the hardcopy logfile) but does not otherwise impact what is placed into the instruction's response buffer.
The default is?DISABLE NOECHO
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Yes, its possible. Is it advisable?
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Joe
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On Sat, Nov 19, 2022 at 11:06 AM Bertram Moshier <herc370390vm@...> wrote:
Hello,
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I'm wondering if it is possible for a VM machine / CMS program to have Hercules change tapes?
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I'm working on the VM Backup idea.? My thought is it would be great to automate the backup procedure by having the program have Hercules swap the tapes.
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I know this would not be possible with real iron, but might be with emulation
