Re: [Re: Expensive op codes]

"David Morris" <dmorris@plumcreek.com> wrote:
> Mark,
> 
> The big difference is caused by the setll that accompanies the READE.  
> You cannot block a file that has a setll against it.  
>
As I see it reading blocks (more than 1) record at a time is only useful if
the data has been physically sorted (not logically via an access path) into
the exact sequence the program needs.

In any case I understood (perhaps wrongly) that the disk I/O controllers
pulled whole cylinders of data into memory.  The cylinders could have multiple
records depending on the ratio of record length to cylinder size, or even data
from totally unrelated objects. It depends on how fragmented the file data is
actually on the disk ( maybe we need Norton Speed Disk).

I occasionaly use the old 'SORT, READ(input only),MATCH transactions, WRITE to
temp file(output only), COPY REPLACE to original file' technique because it is
still the fastest processing method I know for lots of data that changes a lot
(but only if Reading blocks of records and Writing Blocks is used). oh and
double buffering helps but I dont know how to invoke double duffers on the
AS400.




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