• Subject: Re: Performance solutions through hardware - points to consider
  • From: Ata510@xxxxxxx
  • Date: Tue, 20 Jul 1999 22:07:04 EDT

Hello, 
Several points follow: 

Re: the below, please do not forget to check out IBM's Info APAR II11801 for 
BPCS and AS/400 at OS/400 releases from V4R2 and up. There are some very 
significant SQL performance PTFs that should be obtained where OS/400 is 
doing table scans instead of building temporary access paths or even choosing 
existing logicals for particular SQL constructions used in several BPCS 
programs. Some PTFs are/were in TEST status, meaning contact IBM Helpline to 
receive them if you can't order by SNDPTFORD.

And BPCS at version 6.0 uses SQL statements over standard RPG statements 
(which would get records via logical files) for one reason only -- purely so 
that the code can be ported easily to Unix (Unix has no concept of logicals 
hardcoded in programs used to select certain data from a 'table' and the very 
same ADK action diagrams are used to generate BPCS on AS/400 and Unix). 

Problem is that often, the data models were not reassessed to ensure that 
proper logicals existed to fit anticipated needs of the AS/400 SQL Optimizer 
when code changes occurred - or worse yet, someone forgot to code in a WHERE 
clause that selects only Active records, so the optimizer won't use that 
logical file indexed by Active records, and instead builds one over the whole 
physical file as it executes (in the WRKACTJOB screen if you see lots of 
"IDX-xxx" where 'xxx' is a file name, an index is being built on the fly by 
OS/400). All this is revealed in amazing (horrifying?) detail inside a DBMON 
trace, which remains the single easiest way to sort all this out. 

Bottom line: if you have a performance problem with 1 or 2 (or 10) particular 
programs, and everything else on your system that ever uses SQL is 
humming/screaming along quite nicely -- call the SSA Helpline Technical teams 
for bug reporting. Many performance BMRs on 6.0.04 are complete and actually 
do deliver some much-needed new logical files to speed performance, but 
'squeaky wheel gets the grease'. i.e. -  if you report it as a bug, and are 
willing to provide details and/or DBMON evidence to them that a problem 
exists in SQL or in the code or the delivered logicals, and pursue the BMR 
fix with your SSA rep, eventually the problem will be resolved in the code or 
in a database change. If no one reports it and just exchanges e-mail ideas 
for new logicals on this mailing list, SSA R&D is not going to know its 
broken. 

As regards the CFINT* jobs, you may actually be getting slightly paranoid 
with that statement! Search on the as400service.rochester.ibm.com page on 
"CFINT*" and see what it pulls up, such as the following APAR/PTF list:

Document Description:

o  (1000) not on CUM. 
o (9166) on CUM - Was available as of 06/18/99. 
o (9117) on CUM - Was available as of 04/29/99. 
APAR PTF CUM Description 
MA20579 MF22651 1000 TCP/IP - slow response time 
MA20123 MF21988 9166 JAVA performance degradation when optimized 
MA20035 MF21861 9117 WRKSYSACT causes CFINT CPU % to be inflated 
MA19638 MF22602 1000 QZDASOINIT PJ job looping and will not end 
SA68969 SF99104 1000 Database Group PTF (used to order all Database PTFs via 
SNDPTFORD - PTFs to be delivered on media only) 

And check out this Info APAR: basically the CFINT jobs are part of what on 
various models of hardware will control how much CPU is dedicated to 
interactive vs. batch jobs. There is no big 'secret' here. If you purchase a 
'server model' -- batch processing is going to take precedence over 
interactive. If you size your system for BPCS Full Client Server, and later 
in the implementation project decide to switch to Mixed Mode, or suddenly 
switch to 'green screen' COM instead of GUI COM - expect to take a hardware 
performance hit if you had opted to buy a server model system  and forgot to 
consider the workload switch when you decided to implement the software in a 
new way. So, be aware of this when choosing systems and deciding which kind 
of BPCS version 6 to implement!! The newer models of hardware are supposed to 
be more forgiving this way (700 series) -- but it seems there is paranoia and 
misunderstanding being spread here in the mailing list regarding IBM trying 
to 'pull the wool over your eyes' about performance. It sounds more like you 
are not understanding how the hardware is supposed to work if you read this 
APAR: 

APAR#: II09200 
Component: INFOAS400 - AS/400 Information 
Release(s): R360 

Abstract
IMPACT OF INTERACTIVE WORK ON SERVER MODEL PERFORMANCE
CFINT1 CFINT2 CFINT3 CFINT4 TASKS

Error Description
IMPACT OF INTERACTIVE WORK ON SERVER MODEL PERFORMANCE
 ______________________________________________________
 
 The  performance  of  the  server  models  are optimized for
 client/server and  batch  environments  at  the  expense  of
 interactive  environments.  This  means  that as interactive
 work is added to the server models, the overall system  per-
 formance decreases. In environments where only client/server
 or  batch  work  is  present, the effective performance of a
 server model is represented by the non-interactive RPR.
 
 However, for mixed environments, the  effective  performance
 of  the server model is represented by the range of the non-
 interactive and interactive RPRs, depending on the amount of
 interactive work present. If the interactive CPU utilization
 is at most 2% to 10%, the overall performance is represented
 by the non-interactive RPR. This means that the  performance
 of  both interactive and non-interactive work is represented
 by the non-interactive RPR.
 
 However, if the CPU utilization of interactive work is  more
 than  about 2% to 10%, the overall performance decreases for
 both interactive and non-interactive work until the perform-
 ance of both is represented by the interactive  RPR.  There-
 fore,  maximum  price/performance  of  the  server models is
 achieved when interactive work is kept to a minimum.
 
 On some performance reports, additional tasks are listed  as
 compared  to V3R1. The CFINTn task, where n is the processor
 number (1, 2, 3, or 4), processes all of the  interrupts  on
 the machine.
 
 o   On  the  traditional  models  (models  400, 500, 510 and
     530), the time spent in CFINTn may be only  a  few  per-
     cent.
 
 o   On   the   server   models   (which  are  optimized  for
     client/server work), the time spent in CFINTn  increases
     significantly  as you add more non-optimized work to the
     system.
 
     For example, when the CPU  utilization  for  interactive
     work (i.e. non - optimized work) on a 50S is 2%, the CPU
     utilization  for CFINTn is only 4%.  As the CPU utiliza-
     tion for interactive work increases to 21%, the time  in
     CFINTn  increases  and  CPU  utilization  for CFINTn in-
     creases to 40%.   Finally, as the  CPU  utilization  for
     interactive  work  increases  to  24%, the time spent in
     CFINTn increases further and  the  CPU  utilization  for
     CFINTn  increases  to  64%.    This sizeable increase in
     CFINTn utilization is a direct result of adding too much
     non-optimized work (in this case, interactive  work)  to
     the system.
 
     Note  that  all  of  the  server  models follow the same
     trend, but they differ significantly from  the  example.
     For detailed predictions, use BEST/1.
 
 In  order  to  get  the best price/performance from a server
 model, minimize the amount of non-optimized work on the sys-
 tem.  A rule of thumb is to keep the non-optimized  work  on
 the machine to less than 2% of the total CPU utilization.


Thanks
In a message dated 7/20/99 7:43:18 PM Central Daylight Time, 
fkolmann@revlon.com.au writes:

> 
>  Dwight Slessman wrote:
>  
>  > Is the same job consistently slow or does it run quickly sometimes and 
> slow
>  > other times?  We have found many areas of BPCS that use very poor
>  > programming techniques in general and SQL in particular.
>  
>  Dwight we have a donk that is too big for us.  The jobs times are 
> constsistant.
>  By this I mean it is not the load
>  on the AS400 affecting the job.  It is the job itself.  Other jobs running 
> at
>  the same time as the jobs in quwstion, ECM
>  are flying along.
>  
>  > The As/Set case tool (we have been using since 1992) does not generate 
the
>  > world's most
>  > efficient code to begin with.  Add to that some "creative" techniques 
used
>  > by SSA and you get some real dogs.
>  
>  We are also using AS/Set.  (Is this really a CASE tool?)  I thought CASE 
> tools
>  made programming easier
>  rather than an arcane art.)  Its the SQL that SSA use in place of setting 
up
>  data models, or rather the difficulty of
>  modifying data models and having all programs that use the model updated 
> that
>  may be part of the problem.
>  
>  > We had a sizing problem with our AS/400 and would experience intermittant
>  > performance problems.  If your
>  > performance comes and goes you could also be experiencing a "governing"
> effect
>  > supplied by IBM.When your job appears to "go to sleep", useWRKSYSACT and
>  > check if there are any CFINTxx jobs running and how much CPU they are
>  > pulling.  If you see multiple CFINTxx jobs running and they are pulling a
>  > significant percentage of CPU, you are being slowed down by IBM
>  
>  Ahh my  paranoia is at an end , no headshrinker required (for now anyway).
>  Thanks for the tip.
>  
>  > upgrade.  By the way we are on BPCS 6.0.04 mixed mode with an AS/400 
2178.
>  
>  Thanks DWIGHT, we are also 6.04 MM and  have a 640-2237 on V4R2M0.
>  
>  
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