Storage overlays for multi-threaded servers such as CICS and IMS do exist but are far less than UNIX threading. CICS allows the use of key 9 and programs are usually conversational (vaguely remember that most storage is free while waiting for a terminal response). IMS runs code in dependent regions. While storage overlays are possible, they should Storage ovelays are occasional but are not a common occurrance (I'm guessing).
UNIX also has shared memory but it only has mutex and semaphore for serialization. Far fewer applications take advantage of shared memory than in z/OS. Many products on z/OS take advantage of shared memory. z/OS has tools (enq, cs, locks, plo, ...) and common techniques that are commonly in use. In z/OS, our programmers are less IT aware than than in UNIX. They can be spend more time with their area of expertise because we have many facilities that exist because of shared memory and authorized states. RACF, JES, SMS, GRS, automation, CICS, IMS, databases and many more. Additionally, z/OS is tightly coupled so we share resources between systems (e.g. datasets, disks tapes, sysplex storage). z/OS has builtin functionality that makes sharing invisible. C programmers in the UNIX environment have a lot on their plate. They must be a jack of all trades which can be daunting. They often must build all the things we take for granted. C manuals don't discourage shared storage so such a complicated functionality can easily be inappropriately used by less experienced programmers. It's use is discouraged to avoid the inherent errors that can occur if not appropriately implemented. For applications running in a single CPU environment, UNIX programmers don't need to worry about shared storage. As the number of CPU's increases and considering the use of 64 bit addressing, future growth will probably require threading and using shared memory so that work can run in parallel. Jon Perryman. On Wednesday, May 14, 2014 7:53 AM, John McKown <john.archie.mck...@gmail.com> wrote: Just "blue skying", but I wonder how much it would "cost" to use them in a >highly multi-threaded "server" to enhance reliability. Especially if the >server, like CICS, ran user supplied transaction code. Or is the UNIX way >of using separate processes, in separate address spaces, simply "better" - >FSVO "better". I know some UNIX people who are bemoaning the increased use >of threads in a UNIX environment due to possible cross task memory >corruption. > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
