z/OS uses 16 different Keys to allow/deny access to each 4Kb block of central storage.
Does CA Datacom use Storage Protection Key 0?
CA Datacom mostly runs in Key 8 but briefly gets into Key 0 when needed and gets back into Key 8 promptly. One of the instances would be when using XCF. Also during COVERED VIRTUAL processing to name a few.
IBM Storage Protection Keys: