What is an Architectural Level Set?
An architectural level set occurs when the operating system folks draw a “line in the sand” saying their system will not run on any machine that does not have features “x, y, and z”. The first architectural level set (now known as ALS1) occurred with OS/390 V2R10. The features it required can be found in this list: http://www.ibm.com/servers/s390/os390/plug.html The second architectural level set (now known as ALS2) was not established by technical people but rather by edict from the “geniuses” in marketing. That’s why it backfired and angered so many customers. It occurred with z/OS V1R1. The additional features it required can be found in this list: http://www.ibm.com/servers/s390/os390/plug1.html The next “line in the sand” was the requirement by z/OS V1R6 to run in z/Architecture mode. Some have called this ALS3. All z/OS releases will still run on the original “freeway” (z900) machines and there have been no level sets since. The next level set probably won’t occur for years. When
