It can be surprising to see how much value remains in an operating system that's not been altered in almost a decade. Hewlett Packard Enterprise has 3000 documentation on its website that is still behind a paywall of sorts. Users access this info by validating their HP Passport credentials — the ones that indentify the user as being current on a support contract.
The HPE website has plenty of advice and instruction available without a validation. If you ask, for example, "Can the HP 3000 and GSP LAN configuration be on different subnets?" HPE reports
There are two server platforms (A-CLASS [A400/A500] and N-CLASS [N4000]) that can run MPE, which uses the GSP (Guardian Service Processor) console for offline hardware operations like startup and shutdown of the system, access hardware console or system logs, etc.
It is possible for management purposes to place the GSP operation on a different subnet from the MPE server LAN, thus isolating or protecting either environment from one another. One reason for that can be to prevent normal users from telneting or in other ways accessing the GSP console or the other way around.
Or, another morsel that's useful in the era of declining hardware know-how: A-Class IO path memory configuration guidelines. Useful for the manager who's trying to set up memory cards in one of those $5,000 replacement 3000s.
However, if you'd like to read the most current documents, a support contract stands in the way. An updated NMMAINT listing is behind the paywall. HPE created the document in August of 2019. There's no available support to be purchased from HP for MPE/iX.
The documents that survive can be extensively redacted. A HP3000 License Transfer Process document references a web address no longer in service. The address licensing.hp.com no longer answers to requests.
Some information on MPE/iX at HPE's website is among the 4,386 documents at the site. Having the confidence that it will remain in that place is the next step in learning to rely on HPE resources. Independent MPE/iX resources have been more reliable, although the web pages for MM Support went dark this year.