Re: Service Program Overhead

[CRPence <CRPbottle@xxxxxxxxx>]

  Reading via a keyed access method is "random" I\O which can be 
significantly slower than reading via an arrival [i.e. sequential] 
access method; blocking can be specified for the latter.

  If a VIEW can be used for the unordered access of data, then the 
SQL SELECT statement [directly or in a] VIEW could possibly even 
encapsulate the formatting logic against the data within the I/O 
buffer.  As a SELECT with an ORDER BY the method for ordering can be 
left to the optimizer; e.g. a sort of sequentially read data or data 
read in parallel may be more optimal than keyed\random I/O.

Regards, Chuck

James Perkins wrote:
> Well unfortunately I can't use blocking because I'm using SETTL,
> READE and CHAIN.
>
> I have not tried a view, but that may work thinking about it. If 
> I get the time I might try it. I've already gone over budget due
> to trying all this stuff out, but what are you going do ;-)
>
> Nathan Andelin wrote:
> > I may be able to suggest a few performance tips. To begin,
> > are  you using block(*yes) on the F-spec of your input file?
> > If not, does that improve performance?
> >
> > I'd also be interested in hearing the performance difference
> > between reading an SQL "view", rather than your read + chain
> > sequence.