Add STORAGE(ADDR,MAP) to your IEASYS00 parmlib member. This forces the system to maintain detailed storage allocation maps, making erroneous FREEMAIN attempts easier to trace.
Historically, if you wanted to work with z/OS, you needed access to a mainframe. Since physical mainframes are expensive, IBM released ADCD packages—pre-configured z/OS systems distributed on tape (and later, as massive zipped files).
The workflow was notoriously difficult:
While effective for learning, this model was static. It didn't reflect the dynamic, CI/CD-driven world of modern software development.
Today, the phrase "z/os work" implies something different. IBM has pivoted toward the Z and Cloud Modernization Stack. Instead of downloading a monolithic ADCD, developers now utilize containerized applications and modern IDEs. z os adcd 113 13 work
The new workflow focuses on:
Default ADCD credentials (for academic use) are typically: Add STORAGE(ADDR,MAP) to your IEASYS00 parmlib member
From there, enter ISPF to access the classic mainframe development environment.
Once you have diagnosed the root cause, apply one or more of the following solutions. While effective for learning, this model was static
Use the LMOD (Load Module) command in IPCS to see the failing module's attributes. If the module is not APF-authorized but runs in supervisor state, you have found a configuration problem.
Despite its age, ADCD 1.13.13 provides a full z/OS experience for learning and small-scale testing: