[Simh] attaching a tape virtual file without stopping simulation

[Boucher, François]

>> How can I attach a tape virtual file to the TQ0 simulated device in simh 
>> without stopping simulation with CTRL-E ?
 
>You can't, but you do have 20 seconds to do it before the system(s) will 
>crash with a CLUEXIT bugcheck. When I was doing some experiments, I was 
>able to unload and load tapes in the SIMH console within the 20 second 
>period.
 
>You can also change the SYSGEN parameter RECNXINTERVAL to have a larger 
>timeout.
 
>--Marc

 

 

Marc, you are great!

 

I knew i had a bit of time to do the job before the crash happens. This 20s time frame is about the

same also about disks that are being attached/detached in SIMH while stopping simh.  The major drawback is that it implies

a human has to mount the tape file, and that human has a limited amount of time before the crash will happen.

In the place where I work, where we still have computer operators,  I would prefer an automated attach

process... 

 

I will try the solution of modifying RECNXINTERVAL anyway to increase it's time.  Thanks for your suggestion.

 

I am also inclined of checking if I can get simh by changing source code to automatically always

attach itself to a given file name, but when it detaches itself, to make it rename the virtual tape file,

so the tape file does not get overwritten.

 

In pseudo-code, this would be my idea:

Let's say tape.tap is the virtual tape file. And let's create a simh variable say sim_auto_attach wich could

be TRUE (tape will always have a virtual file in it) or FALSE (actual behaviour).

 

In sim_detach(),

Run function as usual, detach tape metafile from tape device.

If simh parameter sim_auto_attach == TRUE, then  

Rename tape.tap to tape#.tap where # is a unique number (date and time?)

call  sim_attach() with the tape.tap file as the target file argument.

Return()

 

 

It could also be possible to create a parameter with the auto-attach file name, instead of the tape.tap constant.

 

A little auto-critic on my above solution is that this is good for WRITING backup savesets to the tape.

It is not usable for restoring.  Another virtual tape drive has to stay manually controllable to attach/detach

the virtual tape file. 

 

Brian Knittel also makes a very interesting solution, to have at long time intervals (ie .1sec) the simh check

for the existence of a command file that contains commands to attach/detach files.  This command file could be written

With the same syntax as vax.ini for example, and it contents be executed by the do_cmd() function from simh.

 

This would be a great solution to my RESTORATION process, when one would need to have a tape attached

for reading purposes.  Brian's solution is more universally applicable, but might need more human interventions,

than the auto_attach modification.

 

Thanks again, Marc and Brian, I value your inputs very much!

 

Best regards,

 

Francois Boucher ing.

 

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.trailing-edge.com/pipermail/simh/attachments/20080122/6f914bec/attachment-0003.html>