[Info-vax] Tertiary VMB?

[H Vlems]

On 10 jan, 14:44, gerr... at no.spam.mail.com wrote:
> Hello everyone,
>
> the V5.2 version of the "VAX/VMS Internals and Data Structures" (EY-C171E-DP)
> book states the following about cluster members booting over the Ethernet:
>
> "NISCS_LOAD can be thought of as a VMB extension. It contains a minimal class
> driver and several Ethernet datalink drivers. Using the class driver and the
> appropriate datalink driver, the satellite can access the secondary bootstrap
> file, normally SYSBOOT, on the system disk served by the host. The minimal
> class driver and Ethernet datalink driver present a standard disk interface,
> allowing SYSBOOT and the rest of the boot procedure to execute as though
> performing a normal disk boot." (§ 30.3.4.1)
>
> "The secondary bootstrap program, SYSBOOT, executes when VMB is directed to
> load a VMS system. VMB, having already tested main memory, reads SYSBOOT into
> memory and transfers control. (When booting over the Ethernet, VMB loads
> NISCS_LOAD and NISCS_LOAD loads SYSBOOT.)" (§ 30.4)
>
> About the same topic, Digital Technical Journal has the following:
>
> "SYSBOOT program could not be loaded directly by a MOP exchange. SYSBOOT
> expects to be able to access the boot device as a block-structured storage
> device; it does not understand the various types of Ethernet adapters that may
> be present. Moreover, SYSBOOT would not have enough information to locate the
> system disk. Therefore, another image called NISCS_LOAD is inserted into the
> boot sequence between VMB and SYSBOOT. NISCS_LOAD provides the environment
> that SYSBOOT needs to do its job correctly." (Vol. 1, n. 7, Sept. 1987)
>
> However, while reading various cluster manuals, I've found many references to
> TERTIARY_VMB.EXE, a file which is not mentioned in the above paragraphs. So,
> I'm trying to understand where in the process it stands, which are its
> functions and possibly when it was introduced. I think It should be something
> used before SYSBOOT receives control. Maybe it is loaded by NISCS_LOAD before
> SYSBOOT. Does anyone here have some details about that?
>
> Many thanks,
> G.
>
> P.S.: I'm a Hobbyist with an interest in internals :-)

If you're still interested I can have a look at one of my VAX systems.
Off the top of my head, the tertiary loader is used only in network
boots.
If DECnet phase IV is used to bring a satellite into a cluster, I
guess the process looks like this:
VMB.EXE lives in local ram on, say, a VAXstation. It knows that if the
bootdevice is set to ESA0 that
it needs to send a network message that includes its own MAC address.
All VMS systems that have the
service attribute enabled on their DECnet circuit(s) will use the MAC
address to check whether it is in their
node database. If so, the secondary and tertiary loaders are run.
Both image names may be specified in the DECnet database.
I suppose there must be a guide to local area vax clusters that covers
this topic, or perhaps the cluster management manual?
Hans