There's a ton of information on IBM mainframe programming, they're the IBM redbooks. They're all here: https://www.redbooks.ibm.com/domains/zsystems https://w

There's a ton of information on IBM mainframe programming, they're the IBM redbooks. They're all here: https://www.redbooks.ibm.com/domains/zsystems https://www.redbooks.ibm.com/domains/zsystems IBM's mainframes have some of the best technical documentation for any product line, anywhere, and if you can't find what you're looking for in the redbooks, the expensive support contract that you likely got with your z/Series comes with support that's sometimes described as... aggressive at solving high priority incidents with their internal support databases. There's also the online manuals that come with z/OS, and you can get a free account via z Xplore: https://www.ibm.com/it-infrastructure/z/education/zxplore https://www.ibm.com/it-infrastructure/z/education/zxplore You can also get a Linux LPAR on a s390x machine (LinuxONE, basically a regular mainframe with the processors fused to only run Linux) as part of the free tier on IBM Cloud. That being said, most real-world deployments have a ton of other stuff running on top of the OS, usually from Broadcom and other close software partners, and dealing with those packages usually requires a support account with those companies as well. The applications themselves are very weird if you're not used to living in a mainframe environment. For example, you can get PKZIP for z/OS, and there is a 437 page PDF describing just the error messages alone. Generally, learning how to get around in a mainframe environment requires working in a mainframe shop, nearly all of which are very mature and have converged on certain ways of dealing with testing, deployment, upgrades, migrations, etc. These procedures are usually not documented because they're simply well-understood by all the staff, or it would be dangerous for them to be working in the mainframe environment. Learning to use just ISPF, the closest thing z/OS has to a management shell, requires not only learning ISPF, but also all the installation-specific details for a given environment.