RE: data area question - performance

Barbara,
Regarding the performance of using data areas.

We still use data areas to increment unique numbers (I know that V5R2 identity 
columns a now worth a serious look).
However, when the iSeries is under heavy load (90% up) because of poor 
performance in certain applications, it appears that we get problems with 
completely separate jobs because they cannot get a lock on a data area. Since 
the data areas are often not related to each other from an application 
perspective this may be just a consequence of too much CPU load where there is 
some low level code that cannot grab an release a data area fast enough.

I have always been under the impression that data areas are objects designed to 
be so simple that they lend themselves readily to processes that require the 
rapid update of a value such as a counter by multple processes. It has been 
suggested to me that using a file would eliminate such a locking issue but am 
very suspect of the overhead (for system data management processes) and 
struggle to believe that anything can be faster than a data area especially if 
the input/output statements are consecutive lines of code.

Peter

-----Original Message-----
From: Barbara Morris [mailto:bmorris@xxxxxxxxxx]
Sent: Thursday, May 29, 2003 11:31 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: data area question


"Shrader, Patrick" wrote:
> ...
> Code (V4R5):
> D period         uds                  dtaara(PROCYR)
> D  cmonth                        6s 0
> ...
> Data area definition:
>                                Display Data Area
>                                                              System:
>  Data area . . . . . . . :   PROCYR
>    Library . . . . . . . :     FILLIB
>  Type  . . . . . . . . . :   *DEC
>  Length  . . . . . . . . :   6 0
>  Text  . . . . . . . . . :   Processing Year and Month
>  Value . . . . . . . . . :   200312
> 

Patrick, by putting the DTAARA keyword on the DS line, you've defined it
as a character type.  Put the dtaara keyword on the numeric variable
itself.  You can't code the U since it's not a DS, so you'll have to
read and write it yourself using IN and OUT.

D  cmonth          s             6s 0 dtaara(PROCYR)

 * If you just want to read the value:
c                  IN     cmonth

 * If you also want to change the value:
c     *LOCK        IN     cmonth
   ....
c                  OUT    cmonth

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