Bill Lancaster wrote:
>The two top metrics in evaluating this is Read Hit Percentage (the
>percentage of all read I/O's satisfied in RAM) and CPU Busy on Memory
>Management.

I would add a couple of comments to Bill's advice.  First of all, a poor 
read hit percentage is not necessarily indicative of a memory shortage.  It 
could easily be the result of poor data locality or very random retrievals.  
Of course, these are measures of overall system activity, not a specific 
process, so Bill's rule of thumb is valid in most cases.  Other indicators 
not mentioned are Memory Manager I/O and page faults.

Dave Waroff wrote:
>MPE performance strikes me as almost the inverse of a traditional virtual 
>storage system where plentiful I/O is substituted for
>scarce memory.

Not at all!  In fact, that "traditional virtual storage system" is exactly 
the issue.  As more and more of the data structures that are "virtually" in 
memory fail to fit into physical memory, more swapping must take place, and 
processes must wait for those swaps to complete.  When you increase physical 
memory the overhead of managing virtual memory goes down.  I/O is typically 
the bottleneck in a memory-starved system, hence my comments about memory 
manager I/O and page faults above.

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