Yes, this is certainly true, but one could, in principle construct a Rexx multithreaded exec that issued the 10 CPFMTXA command, one per thread (assuming CPFMTXA can execute in such an environment, I don't know). When multitasking features were added to CMS (in the early 1990's, I think), it became possible for CMS to spawn background tasks, similar to what Linux can do. I believe that Chris Casey at IBM Endicott even got a patent on the method CMS uses to do this, but for some reason, IBM never externalized that interface or documented it.
The paradigm of using multiple virtual machines to accomplish work in parallel, as per your examples, is used simply because it works very well in this environment. I would posit that your example of having 10 background CPFMTXA tasks running in one Linux guest would take longer (wall clock time) to finish than 10 separate virtual machines, each running CPFMTXA, because there are more opportunities for CP to schedule the execution of 10 virtual machines than just 1. (And, no, I can not prove this last statement....) Another reason many of the common VM services (DIRMAINT,e.g.,) is due to the fact that they were first designed and coded when CMS was indeed a non-multitasking, non-multiprocessing o/s. If being done for the first time theses days, I would suspect that they would be designed to take advantage of the newer features in CMS to reduce the need for worker machines. The new LDAP server is one such example. As others have already noted here, converting from CMS managed system support for VM to Linux-based system support is a huge undertaking, with little or no payoff at the end. Let CMS do what it does best and let Linux host the heavy duty applications it was designed for. Morris, Kevin J. (LNG-DAY) wrote:
How about a simple example: Lets say that I want to add 10 3390-3's as page space to my zVM system. I login as MAINT and issue the CPFMTXA command to format the first volume. The MAINT userid is now tied up for 5+ minutes while the volume is formatting. Plus I can only do one volume at a time. Now, I can simulate multitasking by logging on as 10 different MAINT users (assuming they are already defined in the user directory and ESM) and have each one format a volume. Contrast this scenario to Linux where I can issue the same command 10 times and simply send all of the processes to the background without tying up my userid/interactive session, and all of the volumes are formatted simultaneously. Several other examples: The REXEC server uses secondary virtual machines (agents) to execute commands passed from each ANONYMOUS or GUEST client. This allows the REXEC server to better service multiple REXEC requests, as the multiple agents accessible to the REXEC server help simulate a multitasking environment. DIRMAINT has its DATAMOVE service machine. IBM Operations Manager uses multiple "worker machines" to propagate work.
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