IBM AS/400 and iSeries: PowerHouse Performance Question

[David Morrison - Corporate]

Conrad,

Thanks.  This is very insightful.

We leave most of our data files open, as you say; there are only a few places where we explicitly close them.

So, if a user sometimes needs to access a file for read-only purposes and sometimes for read/write purposes, it would be better if they always opened it for read/write first, then, correct?  

We have tried to write our programs to specify read-only, whenever that is the case (by making DESIGNER files OPEN READ, for instance, and using REFERERENCE files whenever possible), in the interest of making programs run smaller and faster.  Have we been using the wrong strategy?  

Maybe we should look at the files that a given user is likely to need for read/write purposes, and deliberately open them that way in their opening QUICK program, to reduce the number of open data paths that they will eventually use, in their session?

Thanks.

David Morrison
McBride Electric


-----Original Message-----
From: Whittall, Conrad [mailto:Conrad.Whittall@Cognos.COM]
Sent: Thursday, December 12, 2002 10:12 AM
To: David Morrison - Corporate; powerh-l@lists.swau.edu
Subject: RE: IBM AS/400 and iSeries: PowerHouse Performance Question



Once PowerHouse has opened a data file it keeps it open and reuses the
connection for other screens that access the same file...so long as the
original open mode is compatible with what other screen programs want to do.

For example, if screen A opens file X for read/write access  (maybe a
PRIMARY, DETAIL, SECONDARY or DESIGNER file) and then later screen B needs
file X as a read-only REFERENCE file, PowerHouse will not open the file
again but simply reuse the existing connection. If the user accesses screen
B first, then file X will be opened for read-only access. If they then
access screen A then file X will have to be opened a second time...this time
for read/write access.

So, once a data file is open it is unlikely that PowerHouse will need to
open it again (unless the designer has explicitly asked for a program to
close it using the CLOSE option of the FILE statement. However, a program
file is opened each time it is called (although your operating system might
cache these files depending on how often they are being accessed, and so a
PowerHouse access might not necessarily mean a disk access).

Given all of this it is probably slightly more efficient to have the program
library ahead of the data library on a user's library list...since they will
be opening program files much more often than data files.

Best regards,
Conrad

Conrad Whittall
e-Learning Architect, Global Education Services
Cognos Incorporated, 3755 Riverside Drive, Ottawa, Ontario, K1G 4K9, Canada

-----Original Message-----
From: David Morrison - Corporate [mailto:dmorrison@mcbrideelectric.com]
Sent: 12 December 2002 12:32
To: powerh-l@lists.swau.edu
Subject: IBM AS/400 and iSeries: PowerHouse Performance Question


We currently keep our Production programs and data in the same library.

We're thinking of splitting them into two separate libraries.  Does anyone
know if this will affect interactive and/or batch performance of PowerHouse
programs?  And, in which direction?

If we make this change, would it be better to put the program library ahead
of the data library, in the users' library list?

Thanks.

David Morrison
McBride Electric
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