• Subject: Re: Performance solutions through hardware
  • From: fkolmann@xxxxxxxxxxxxx
  • Date: Tue, 20 Jul 1999 13:05:28 +1000




> I have recently been to several IBM classes & the instructors still define
> INTERACTIVE = Human being interacting with the computer, whether twinax or PC
> is the work station
> BATCH = the job is running without a work station in the picture, like off of
> a JOBQ

Thanks for the defnition Al.  I see nothing has changed.  We certainly use 
QINTER
QBATCH sbs
as they should.  I have started from S3 cvtd to S38 Cvtd to AS400 so I am
familiar with all AS400
concepts.


> >  To be precise,
> >  if a programmer reads an entire file sequentially to update a record
> >  rather than using a logical file to get to just the record that needs
> > updating, how will changing the CPU fix the problem.
>
> In this example, the correct solution is through software, although hardware
> can make the extremely inefficient process get done sooner.
>

Thank you for your reply. My point is that with SQL many programmers are not
setting
up appropriate indexes thus forcing  DB2/400 to create and destroy indexes on 
the
fly for each
get or update of a record via SQL.  It is the ease with which SQL allows such a
condition to occure
and the careless approach of some coders, as evidenced by the actual code that 
is
the problem.
Luckily the AS400 DB has a ability to hunt for access paths the can facilitate a
query.  This function
was not in the early AS400s and one had to be very careful about Indexes (lgl
files). Today it seems
that code gets written and only when the user has a problem are the LGL files
created. No one
has explicetly told us this is the case.  This is not to mention IBM bugs (that
have been since fixed) where the
optimisating (hunting) logic did not find the optimum index.


>
> > knew a thing or 2 but this stuff is like the X-Files to me, or am I paranoid
> again.
> Some jobs may appear to be in a wait condition if their access to system
> resources have a low priority.  Check out the rules in *JOBD for the JOBQ a
> batch is in.  This sort of topic is covered by IBM AS/400 classes in System
> Operator, Work Management, System Administration etc.
>
> http://www.training.ibm.com/ibmedu/spotlight/as400.html = IBM's curriculum on
> AS/400 complexities
>
> Al Macintyre

Thanks Al , you reply has restored hope to me.  I know all the stuff about JOBDs
JOBQs CLASSes
SBS  ROUTING ENTRIES priorities etc.  I know about disk arms and DB access
positioning files for optimum acceses ,
sorting into most used sequence and buffering(double or otherwise).  Thats what
makes the problems that
SQL causes so hard to understand.  SQL has the coding methods to avoid poor
performance, but it is very
easy to cause poor perfromance with SQL.


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