Re: Record blocking optimization -- RPG400-L

Hi Rob,

It will only work this way if you are doing matching records processing. Otherwise it will work like this

Dow Not %EOF(primary) Read primary; // Calc specs EndDo; Dow Not %EOF(secondary) Read secondary; // Calc specs EndDo;

Yep, you got it!

And, honestly, I am not sure if it does the calc specs (the first time) before, or after, the read. I remember doing something like putting a record identification indicator and conditioning the calc specs on that indicator. I have an old RPG coding template that might show me this.

The calcs are done after the read, but there's a pre-read too! I really wouldn't recommend getting into it for somebody new to the language. When I was teaching RPG/400 when the AS/400 was new, I usually talked about RPG-II a little bit, because most of them would be working with RPG2 programs in converted S36 shops. Not anymore. The cycle was still often used, and OPNQRYF took care of primary file preparation, etc, so I talked about it. If I taught it again, I might very briefly cover that in case they come across one, but not much.

I think there would be a flowchart in the RPG-LE reference manual that lays it out exactly, because the compiler still generates code like that, but for most people they need that explained too! It can get complicated pretty fast, it's impressive how much coding the compiler generates for you when using the cycle.

For the most part instead of using the cycle, I generally use SETLL and READE and using externally described data structures generally meets the needs that may have made the RPG cycle useful otherwise, because I can prefix them as a sort of "pre-read", and move the data structure to another based on the same PF to do "detail time" processing.

D PreviewRecd  E DS  extname( FileX ) prefix( in )
D ItemRecd        E DS  extname( FileX )

And Alan, it's not just COBOL programmers.  I sent some code to Jon Paris and 
it stumped him for quite awhile too, until he realized that it had a  primary 
file.  It's just not something that's assumed anymore.

Rob Berendt

That's caught me a couple times recently too.

Alan

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