Re: Need ideas to reduce open/close in RPG program

On 14-Dec-2015 11:49 -0600, Vinay Gavankar wrote:

So if I were to have a subroutine upfront, which does a OPNDBF for
all files with SHARE(*YES), I could leave rest of my program
unchanged?

Essentially, yes. The Open Data Path (ODP) created by the Open Database File (OPNDBF) must be /compatible/ with the open by the HLL program; so for example, if the RPG open is keyed Access Path, then the default [though best to specify explicitly] ACCPTH(*FILE) will match; similarly the COMMIT specification, and there may be some others not as easily controlled, for which sometimes a C open might be better to avoid warnings or to overcome errors when the OPNDBF can not effect a compatible ODP to be shared.

I have following statements already in the program:

Close FILEA;

CMD = 'OVRDBF FILE(FILEA) TOFILE(*LIBL/' +
FILNAME(S) + ') LVLCHK(*NO) SHARE(*YES)';

If the Record Format (RCDFMT) is the same for the different files, the turning-off of the Level Check (LVLCHK) feature is unwarranted, and even potentially problematic for lack of notification if anything had changed unexpectedly. Also, the lack of an Override Scope (OVRSCOPE) specification is a potential problem; the parameter has a default value that could be changed.

CALLP(e) SYSTEM(CMD : %len(CMD) );
OPEN FILEA;

I could leave all these unchanged and my performance would improve?

Yes, because all of the existing as-coded Open and Close activity since would be performed against the /shared open/ that was created by the newly-coded Open DataBase File (OPNDBF), rather than continuing to create a new ODP for each OPEN and destroy that just-created OPD for each CLOSE. Effectively, instead of the inherently expensive create\destroy of /objects/, the code runs a streamlined path whereby the create\destroy activity is replaced by the inherently inexpensive increment\decrement processing of a variable; of course there is still a bunch of [unnecessary] external calls being made to the Data Management and routed to the Database to effect the updates to that counter variable [counting the number of shared opens], but to no longer create\destroy the temporary ODP will be a noticeable saving [although not nearly as beneficial as would be the case, if the create\destroy was for a permanent object per that being an immensely more expensive process involving assigning an owner and private authorities].