Re: Separate program for File retrieval

First of all, you don't have to move I/O to a separate module to remove the
need for recompiling.

You could simply mandate that no program access through the PF and instead
uses a LF with an explicit format. New fields can be added to the PF but
not added to any existing logical. Thus no programs would need to be
recompiled. Programs that need the new field would be modified to use a
newly created logical that includes the field. ( substitute SQL
tables/views/indexes as you wish)

Having said that, a DB module is a good idea, as long as it's done right.
By that I mean you don't just emulate RPG op-codes with your own procedures
and a DS from the file itself. Instead, the procedures should encapsulate
business logic.

Instead of
custDS = CUSTOMER_read(1234);
if custDS.credit_hold <> *ON;
//allow customer to purchase
endif;

You'd have
if not CUSTOMER_OnCreditHold(1234);
//allow customer to purchase
endif;

Personally, I think it's worthwhile to have to have a couple of layers.
Consider an INVENTORY *SRVPGM, I'd have modules named
INVENTORY - contains all the publicly exported procedures for the *SRVPGM
IVBINMAST - contains protected & private functions that operate on the "bin
master" table
IVMAST - contains protected & private functions that operate on the
"inventory master" table
IVTRNHIST - contains protected & private functions that operate on the
"inventory transaction history" table
...and so forth.

INVENTORY_MoveItem() would be a public procedure that would make calls into
protected procedures for the various tables.

Charles


On Fri, Jun 30, 2017 at 7:32 AM, Vinay Gavankar <vinaygav@xxxxxxxxx> wrote:

At my client, people are kicking around the idea of having a separate
program (module) that will do any required I/O. Existing files already have
tons of programs using them, so it would be done only for new files that
get created.

The idea is that by doing that, if and when a new field is added to the
file, you shouldn't have to recompile existing programs, unless they
require the new field.

Nobody of knows what would be the performance implications of doing it.

Client does not allow compiling files with *lvlchk(*no) and any new fields
are not necessarily added at the end of the file (they want keep the Audit
Stamp fields always at the end of file).

Questions I have is:
1. Is it feasible
2. Is it worth it from performance enhancement/degradation standpoint
3. If yes, how would you actually code it (in RPGLE) so that all programs
need not be recompiled.

Thanks in advance for any advise.
Vinay
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