On Tue, 23 Feb 2010 11:24:55 -0500, David Andrews wrote: >didn't bare MVT have a horrendous core fragmentation >issue?
Suppose that you have a 768K machine and the memory is mapped like this (I'm making up these numbers, and I don't remember where everything was located): 0-200K Nucleus 200K-600K 600K-640K SQA and CSA 640K-768K LPA All your initiators run in the area from 200K to 600K. Suppose you start a job that needs 110K. It gets the area from 200K to 310K. While that job is running, you start another job that needs 200K. It will reside from 310K to 510K. After the first job ends, there is a total of 200K available, but it is not contiguous. You can run a job that needs 110K and one that needs 90K, but nothing larger. At the MVT shop where I worked, we had a fixed number of initiators that each had their assigned Job classes. To ensure that storage would not be fragmented, we had region size standards for each job class, and all job classes for a particular initiator were required to use the same region. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
