Mark Zelden wrote:
An unused unit of storage must be examined, determined
that it is unused and actions (statistics) are taken
for unused storage. If this storage is just not there,
less activity is needed.
But there should be less paging and hence reduced paging overhead.
There's over allocating and then there is OVER ALLOCATING. This isn't
your father's MVS. 64-bit is a big place and changes have been
made to how storage is managed - some of which has caused overhead
issues. In z/OS 1.8 you can have up to 4TB on a z/OS image - prior
to that the maximum was 128GB. Will it matter if you allocate 10GB
instead of 8GB... no, but just because your new z9 came with a bunch of
extra storage doesn't mean you should give your non-paging 8GB LPAR
30GB. Especially if you are in a shop that likes to run your CECs
at or near 100% all the time.
IMHO this ROT is completely unrealistic. Let's imagine a system with
8GB, paging is almost 0. Then we add memory up to the moment of
"absolutely 0" of paging. Let's assume it's 10GB. Or 12GB if you want.
Then every GB added is overallocated.
So, let's add some memory, a lot of to feel the difference: 50GB.
10+50. Six times more than you need.
IMHO the difference between 10GB and 60GB won't be perceptible, while
difference between 8 and 10 GB will be small but perceptible.
Last but not least: Who is willing to add 50GB of unneeded storage???
My $0.02
--
Radoslaw Skorupka
Lodz, Poland
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