On 10 November 2017 at 17:05, Mitch Gallman <mgallman@xxxxxxxxxxxx> wrote:
I have a service program with many exported functions/procedures and I have a copybook with all the prototypes (no /if defined declarations).
If my program only uses one function from all the prototypes that were included...does having the extra prototyped functions that are never used impact startup performance of my program?

Here is what I tell my colleagues when they ask me a question like this.
1) Do you have a pass/fail standard you can apply to the situation?
2) Have you measured the program in question?

Bear in mind The One True Thing about performance questions: Every
action takes time to perform. 'Actions' fall into two broad
1) Required in order to satisfy the business function
2) Optional/convenient to the programmer/database/operating system

Only measuring the actual performance of the programs in question will
tell you where the cycles are being consumed. That said, the general
answer is no, the unreferenced prototypes don't slow program start-up.
But activating a service program with a lot of static variables might.
But before embarking on a project to break your large service
programs into multiple, smaller ones, I beg that you measure the
performance and use solid numbers to make decisions with.

I've been doing performance tuning since the System/38 days, and I
can't tell you how many times my instincts were flat out wrong (just
this morning), and I only found out the real issue after measuring the
performance. https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_73/rzahx/rzahx1.htm


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