> Most of the results are on IBM's own website, and even that contains only high-level details. As other people have stated in this thread, IBM Redbooks are wh

> Most of the results are on IBM's own website, and even that contains only high-level details. As other people have stated in this thread, IBM Redbooks are what you need and they span the whole range from high level overflow to low level. The ABC's of System Programming is probably where you want to start, there are 13 volumes I think. https://colinpaice.blog/2020/06/22/whats-in-abcs-of-z-os-system-programming/ https://colinpaice.blog/2020/06/22/whats-in-abcs-of-z-os-sys... You just have to know what to look for to find low level stuff - for an example, here is the reference for IBM's High Level Assembler Language (HLASM). https://www-40.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R3sc264940/$file/asmr1023.pdf https://www-40.ibm.com/servers/resourcelink/svc00100.nsf/pag... > And if there are, then why is there so little info for them on the web? Is the knowledge proprietary and secret? IMO it is just a cultural thing. A lot of mainframe developers and especially the experts who have deep knowledge have been programming for a long time. Like, started on punch cards while they were getting a math degree. The IBM culture has always been comprehensive documentation available from the source and predates the internet by a few decades, so the kind of public stack overflow culture we are used to never developed over there. The book Hackers: Heroes of the Computer Revolution by Steven Levy kind of talks about this, the difference between the mainframe guys and the mini computer guys. Its a good read. Mainframe people are descendants of the "high priests" that worked on computers before the invention of the mini computer and the culture reflects that to this day.