Re: Can files be opened local to a "subprocedure"?

It is perfectly possible to have subprocedures with local files. OIn fact it is the only way yo get true recursion in a file handling subproc.

The problem is the overhead of the open/close that will occur with each invocation level. Can shared open reduce the load and still allow individual cursors for each invocation level? I don't recall and haven't time to play. Last time I worried about this was in about 1998!

Anything else though is going to require you to manually reposition the cursor upon each return. Just like in the "good old days" of MDT programs and non-persistent CGI programs.

Depending on the performance profile you need you may be able to get away with local files - they certainly offer the "cleanest" most obvious solution.

Just a note on the use of a STATIC file - this works fine but you do need the cursor repositioning logic and may need to have a special call to close the file if you cannot rely on the end of the AG to achieve this,


Just a few thoughts


Jon Paris

On Oct 10, 2021, at 5:18 AM, Roger Harman <roger.harman@xxxxxxxxxxx> wrote:

I use it this way for some service programs.

I typically also use USROPN. I call it with *LOVAL in the first parm (regardless of its intended usage) to initiate the open and any setup I need.
Then it gets called with parms as needed during processing.
At the end, the first parm gets passed as *HIVAL to initiate a graceful close and cleanup processing if needed.

It's a methodology that has worked well for me.


-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Vern Hamberg
Sent: Friday, October 8, 2021 9:03 PM
To: rpg400-l@xxxxxxxxxxxxxxxxxx
Subject: Re: Can files be opened local to a "subprocedure"?

Thanks, Roger, I'd forgot that - have never needed to use it, so,
brain-drain, perhaps!

Vern

On 10/8/2021 9:56 PM, Roger Harman wrote:

Unless you use the STATIC keyword....



-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Vern Hamberg
Sent: Friday, October 8, 2021 6:00 PM
To: rpg400-l@xxxxxxxxxxxxxxxxxx
Subject: Re: Can files be opened local to a "subprocedure"?

Well, so far as I know, when a file is defined in a subprocedure,
basically you have a fresh open when the SP is called, and a close when
it exits - nothing is maintained between calls.

USROPN gets the same behavior - again, so far as I know.

Vern

On 10/8/2021 7:38 PM, James H. H. Lampert via RPG400-L wrote:

On 10/8/21 5:27 PM, Vern Hamberg wrote:

Now are maybe there issues of maintaining the position where you left
off in one of the files?

Of course there are. The record contents can be thrown out (the
recursion is very close to strict tail-recursion), but the position
and the EOF state can't. That is the whole point of the question, and
why opening it locally to the procedure invocation appears to be the
only way, short of caching the entire contents of the file.

And performance is not an issue. The file to be opened locally has an
absolute maximum of 55 records, and an absolute maximum of 49 records
that would satisfy the key conditions.

So far, in my tests, it appears that (at least at V6), simply moving
the F-spec to procedure level requires me to treat the file as
program-described, and define a structure to receive the record, but
treating externally-described files as program-described is old hat
around here. Apparently scatter-gather doesn't work for files declared
at procedure level?

--
JHHL

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