Re: RPG Open & OPNDBF

Kurt Anderson wrote:

I have a CL that does this, and my understanding is that it
establishes an access path.
OVRDBF FILE(FILEA) OVRSCOPE(*ACTGRPDFN) SHARE(*YES)
OPNDBF FILE(FILEA) OPTION(*ALL) OPNSCOPE(*ACTGRPDFN)

And in this RPG program, it Opens and Closes FileA repeatedly.
Obviously opening and closing a file is a performance hit (heaven
forbid we do it a million times). I was wondering how significantly
the previous CL commands affect the RPG Open. Does the performance
on the Open become negligible?

I'll end up changing this so the file doesn't constantly open and
close (because that just doesn't seem like good coding practice to
me), but if there's a performance gain to be had, the priority of
the change will likely be escalated.

Of course that needs to be a CLLE versus CLP, to open in\to the same named activation group as the RPGLE. Having changed to use the shared open technique, then 1M opens becomes 1M shared-open requests [with ODP compatibility validation and Data Management & Database OPM calls, so all the overhead that entails]. As Simon suggests, not negligible; but significantly less impact as compared to using 1M full open\close pairs. Obviously the better choice is to perform the open once, perform all of the 1M I/O, then close once. So do plan to correct the program, rather than trying to effect improvement by using shared opens to decrease the overhead & side effects of full opens. An override to share, should only be done as stop-gap; being fully aware of the scoped open, the requirement to close and the possible need to RCLACTGRP, since RCLRSC will not close the file if the CLLE does not CLOF.

Regards, Chuck