Hi Vic,

I clicked on ACTIVATE, selected the key file but nothing changed.

I got this one by mail this one: 

InterSystems IRIS Server for x86-64 (Microsoft Windows):256
Natural Language Processing (NLP), Sharding, Enterprise Cache Protocol (ECP)


Same with  the Demo Key I downloaded worked fine:

LicenseCapacity=InterSystems IRIS 2019.1, Enterprise:64, Concurrent User, Platform Independent

I'm wondering which license server is referred with a stand-alone installation.
I feel lost.

"cautionary M tales" is really ages old and outdated.

But see it from reverse side: You can run without any change code that was written 40 years ago on PDP-11
I've seen it and can confirm it.
I know of no other system that allows spanning that range of time without touching the code.

But you are not forced to write that style. Or you can even write your code in BASIC if you dislike COS.

Honestly, I never saw an <INVALID OERF> related to a lack of memory.

It typically happens if you do set obj=##class(MyClass).%OpenId(id,,.status)  and do not check for success.

https://cedocs.intersystems.com/latest/csp/documatic/%25CSP.Documatic.cls?PAGE=CLASS&LIBRARY=%25SYS&CLASSNAME=%25Library.Persistent#METHOD_%OpenId

so if you miss if '$isobject(obj)  {  .... error processing  using status....} or similar

then the next access to obj.MyProperty will throw  <INVALID OERF>

Only checking the status will tell you if  you really ran out of memory