IBM Mainframe Forum

Hi,

I just started doing some COBOL code. I just code and transfer from to test environment and then production.
I have no idea how the program works in production. Not the logic of the code. What I'm wondering is how many instances of a program are loaded.
What I guess is that it's a configuration, like program A can have 10 thousand instances loaded, and if more are requested, the requests enter a queue.
Can the configuration be by program?
For example a withdraw program from a bank. Imagine it has like 50 thousand simultaneous access (between the same second). Is it CICS that handle this?
How it would work in this case? And then if a peak access happens, like 150k/sec?
Could you please share a link that explains how theses multiples online requests are handled?

Thank you!

In general, CICS will only have one copy of a program loaded into memory at a time. That program may be executed many times simultaneously by different transactions at different terminals, but (usually) it is still only one copy. It is possible to have multiple copies of a program loaded into memory in CICS, but this is not normally done. Multiple processing of a program is normal in CICS -- find out what reentrancy means -- and CICS limits simultaneous program usage in various ways. These limits include how many simultaneous transactions can execute in a CICS region at one time, along with storage (memory) limitations, and so forth.

These users thanked the author Robert Sample for the post:

tivrfoa (Sun Jan 19, 2014 12:26 am)

As Robert has said, there is usually only 1 copy of a program loaded at any given time, and multiple users of that program each have their own copies of WORKING STORAGE.

These users thanked the author Terry Heinze for the post:

tivrfoa (Tue Jan 21, 2014 8:39 pm)