On Oct 18, 2007, at 6:00 AM, Vernooy, C.P. - SPLXM wrote:
"Barbara Nitz" <[EMAIL PROTECTED]> wrote in message
news:<[EMAIL PROTECTED]>...
The MVS implementation of BPX 'address space creation' was changed
back in the nineties to use RSM shared pages (a virtual overlay of the
creator's address space) because most of the parent address space
pages
were thrown away by the child anyway. That improved performance a lot,
similar to what can be seen in the 'distributed world'. Before that,
'getmain at the given address' was implemented to make the parent
identical to the child in the beginning.
I know the storage part and its efficiency, but creating an address
space is something else, that costs time.
Somewhat off the topic but I feel thats its important to add this. In
the early 80's I was given the task to help out a division get a new
system I was talking with an SE (she was a beginner) and we got into
a discussion of address space create. She was under the impression
that it was no big deal and it was a minor thing to do. In fact she
was suggesting that they set up (IMS? its been a while) that whenever
a transaction was needed that it go through address create. I
suggested to her that she read a little more on the process that is
needed to do a address space create and then come back and tell me it
should be done all the time. She wondered off and (I think) she posed
the question to someone in IBM and they told her that her idea wasn't
so hot and how much it would cost. She came back in a week or so and
said that I had been right. I know she was a rookie and clearly did
not have any idea on the overhead, but she finally got the idea that
it was a lot more than just minor overhead to do.
Ed
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