I tried the D IOS,CONFIG(HSA) command and got a display that did not tell me how big HSA is, but rather how much of HSA is available for adding more configuration changes, such as more control units or subchannels (more commonly pronounced "devices"). HSA stands for Hardware System Area, not Hardware Storage Area as I wrote in my previous post. The info on how many HSAs there are, how big each one is, and its beginning address is all contained in the Service Call Control Block (SCCB), mapped by SYS1.MACLIB(IHASCCB), and pointed to by CVTSCPIN. Service Call is a special SVC (I think it is 122) in MVS that invokes the Diagnose instruction to read hardware configuration info from the floppy disk. I learned about it by perusing some RMF microfiche in 1987. The SCCB also has info on various processor features that are installed, such as the Performed Lock Operation (PLO) instruction. I don't remember any software that displays the SCCB info. TMON/MVS might. It should be easy to build code to find and display the contents or to find it in a system dump that includes (E)CSA and (E)SQA. Since the beginning address of each HSA is a four-byte value (SCCBAHSA), it appears that all HSAs are allocated from the top down of the 2GB bar. Bill Fairchild
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