Re: CPU Increase

Discussion created by ca.portal.admin on Sep 12, 2007
The answer is the infamous ""it depends"". Are you doing an EXPAND PAGE to
just double the page size. Then the amount of I/O will be the same, the
CPU should not noticeably change, same thing for the runtime. If you are
doing an UNLOAD/RELOAD, keeping the same page size but double the number
of pages then you should see twice the number of I/O. This in turn will
double the amount of CPU that is used to get those I/O and since I/O is
usually a large chuck of batch wall clock time, then your runtime is
going to increase accordingly.

There are some other caveats. If you are double the size because the
areas are almost full, then you probably also have a large amount of
overflow records and possibly fragmented records. In this case, if you
do an EXPAND PAGE you will still have the extra I/O for the overflow and
fragment records. If you do the UNLOAD/RELOAD you would hopefully remove
all of the overflow and fragment records. Also, these comments really
only apply to those programs doing area sweeps.

Another issue is that these same batch jobs are rarely as simple as
sweeping a single area. You are usually sweeping one area and processing
other records in other areas. So the increase in runtime, I/O, and CPU
is proportional to just the time the program spends in the area sweep.

I am hoping I didn't simplify this too much, but you can see where this
is a lot involved in this and no easy way to name a 'rule of thumb' that
could be any where close to accurate. If you are not really that
interested in accuracy, just state if you are doubling the area in size
you are doubling the runtimes, I/O, CPU , etc... :-)

Dan Hall
Capital Solutions
Danbury, CT

T 513.217.5060