Re: NBRRCDS and BLOCK(*YES)

[Ken Sims <mr2087@xxxxxxxxx>]

Hi Uma -

> Now, in my case, the file being multi format logical file (of 6 physical
> files), 20 records of which file will be brought into memory ... is it all
> the six files or ???
The documentation does not say, but based on what NBRRCDS does, it would
have to be that many records all from the physical file that contains the
record being read.  The other possibility would be that it would read in
the number of records specified divided by the number of physical files
referenced by the logical.  It would NOT read in records associated with
any of the other physical files.

> forgot to mention in my earlier mail that, apart from select criteria for
> PNO range (so that multiple jobs can be submitted in parallel), ther is
> also another selection criteria which excludes some of the records from the
> file ....
> hence not all records of primary file are being processed (as rightly
> questioned by Martin Booth earlier "You are processing 100% of them anyway,
> right? ")
NBRRCDS will bring those records into memory, even though the logical is
not going to select them (record blocking).

Unless there are a lot of calculations involved with the update program and
your system has multiple processors, I don't think that multiple jobs is
going to provide a performance advantage over one well-tuned job
(well-tuned includes picking a good NBRRCDS value).

Well-tuned also includes such things as not actually doing an update
operation if nothing has changed.  If there are a significant number of
records that are not actually changed, that by itself can provide a very
significant performance enhancement.

Ken
http://www.ke9nr.net/
Opinions expressed are my own and do not necessarily represent the views of
my employer or anyone in their right mind.