1 Jun
2020
1 Jun
'20
12:46 a.m.
On 2020-05-31 21:02, G. wrote:
On Sun, 31 May 2020 14:30:15 -0400, Thomas DeBellis
wrote:
Very similar story as with RSX. However, I wonder if that was kept
maintained in VMS.
It requires that all memory are either core (which don't exist for
VAXen), or battery backed. Battery backed memory certainly did exist,
but I suspect that eventually went out of fashion.
Same on RSX. Either core, or battery backed main memory. The CPU
volatile state is saved at power loss, and execution resumes when power
is restored. Device drivers and programs can get notified about a power
loss and resumption.
Dumping all of memory to permanent storage was never an option, as the
power loss means you only had something in the order of 20ms of
execution time left.
UPSes work on a very different principle. They are meant to be able to
keep the system running for a while when power is lost. And then you can
do a graceful shutdown if needed.
Not sure if VMS have any hooks in place to force a graceful shutdown.
RSX do not, that I can remember.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Can anybody elaborate more on what the VMS power
failure options are?
OPC$CRASH sure looks like a crash, but what happens before the belly up?
You may want to take a look at the VAX/VMS Internals and Data Structures
manuals on Bitsavers where you could find editions for V3.3, V4.4, and V5.2.
There is a whole part (VII or VIII depending on the edition) completely
devoted to the bootstrap process, initialization, shutdown, power failure
and recovery, and so on :)
See http://bitsavers.org/pdf/dec/vax/vms/training/
Quote from the V5.2 book: ?Powerfail recovery support enables a suitably
equipped VMS system to survive power fluctuations and power outages of short
duration with no loss of operation. The support is provided by hardware
features (battery backup) and VMS software routines. VMS support includes a
powerfail service routine that saves the volatile state of the machine when
the power fails, a restart routine that restores that state when the power
is restored, CPU-specific initialization code, and device-specific code
within many VMS device drivers. The VMS software also provides process
notification by means of power recovery asynchronous system traps (ASTs)?.