These info levels are undocumented in the CPS.
Wow. Some of your explanations sounds familiar. After I invested countless hours on reading original Lcmd code, edm2 and all the help files of os2tk45. But where did you get the undocumented stuff from? Answers from some experts in some goups which you noted somewhere? Or is there a place where someone document such undocumented stuff? Stevens site?
Btw: these idiots which wrote the control programming appendum for DosOpenL f.i. should be sent to jail. Again I stumbled over this wrong description and examples (variables versus pointers). It's a mess when the official documentation is so wrong in so many places :-(.
Btw2: It's a somehow educated guess that the file system is faulty here. With different versions of EA handling in Lcmd I very often got 'Trap 000e in JFS'. The last implementation which I think perfectly correct, let the IFS silently stop working only sometimes. Unfortunately I need to copy a few hundred thousand files with a lot of GBs. So still have no simple scenario to reproduce.
Btw3: For my problem I think it's not the DosRead buffer size as this is already limited (<1 - ~16MB) here. AFAIK the problem Silvan reported happens with about 400MB and above. OTOH David explained in the ticket it's not the buffer size which triggers this one known problem, but 2 DosOpenL calls where the first one does nothing. Do you think Davids explanation in the ticket is wrong? Or is he talking about another problem? Is it worth to test with read buffers max. 1MB f.i.?