Re: AS400/i5 etc general behaviour

from david's original question:
How can you manage it? I'm thinking of a program that we have that uses an SQL request that functions normally then suddenly takes a long time to execute.
/
There could be a lot more going on here than memory swaps.
I'd also look at temp access path builds, table scans, and overall
application design.
Previous posts mentioned the Work Management books that layout
i5 memory management. Also add the query analyzing tools (Visual Explain) in iSeries Nav, plus some general application rules to avoid large table scans.
Jim Franz


----- Original Message ----- From: "David FOXWELL" <David.FOXWELL@xxxxxxxxx>
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Sent: Friday, March 13, 2009 4:26 AM
Subject: AS400/i5 etc general behaviour

Hi,

I wondered if I could start a new thread using Alan's reply to the dataq problem.

> ----- Original Message -----
> From: "Alan Campin" <alan0307d@xxxxxxxxx>
> To: "Midrange Systems Technical Discussion"
> <midrange-l@xxxxxxxxxxxx>
> Subject: Re: Multiple Jobs reading from same data queue-who's turn is > it?Job swapping.

If a job is sitting and waiting and gets no activity it is going to swap out to disk and when the request comes in it goes to the job and the job is not available so it swaps it back in memory which takes time. Same problem you run into with Client Access SQL jobs. User stops to take check a figure and when they come back and make another call, the job has been swapped and now they have to wait for it to get swapped back. On a very heavily load system, it is a really big problem.


On a general note :
Alan, how do you get to learn this kind of thing? I'd like to know more about how the system functions, for example, how a program is activated or shared.

As for the example above, I thought that the unique storage address meant that you never knew if main or secondary storage was being used. How would you know for sure that a job got swapped out to disk? Is this information recorded somewhere? How can you manage it? I'm thinking of a program that we have that uses an SQL request that functions normally then suddenly takes a long time to execute.
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