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On 25/08/2006, at 1:25 AM, Haase, Justin C. wrote:
If a system had equal or more main storage than attached DASD, would theonly disk activity be read operations until a shutdown when the system would dump what's in main storage to disk?
midrange.com
Simple answer: No.
Complex answer: No because ...
1) The system writes changed main storage pages to DASD. This happens:
a) when the system has nothing better to do
b) when those changed pages are needed for something else
c) when required to by use of various FORCE attributes on objects
2) Main storage is divided into pools. There must be at least 2 such
pools: *MACHINE and *BASE. Unless these are always larger than needed
for every possible circumstance then one of these pools could become
overcommitted in which case changed pages would be forced to DASD.
3) Jobs use temporary objects and space during operation so they could be consuming more space than you expect. These objects do have to exist in the virtual address space but they don't have to exist on DASD.
4) Jobs are temporary (e.g., batch job starts and stops). When a job ends there will likely be DASD write activity (files closed, changes written to DASD, etc.)
5) Other things I haven't considered ... Regards, Simon Coulter. -------------------------------------------------------------------- FlyByNight Software AS/400 Technical Specialists http://www.flybynight.com.au/ Phone: +61 3 9419 0175 Mobile: +61 0411 091 400 /"\ Fax: +61 3 9419 0175 \ / X ASCII Ribbon campaign against HTML E-Mail / \ --------------------------------------------------------------------
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