The End Is Nigh For CICS

(Originally posted 2014-10-12.)

… and other address spaces, too. 🙂

In Once Upon A Restart I talked about how to detect IPLs and restarts of CICS regions and MQ subsystems (and other long-running address spaces) – from SMF Type 30 Interval records.

It’s easy to see starts but what about stops?[1]

It turns out you can estimate when address spaces stop from the SMF 30 Interval records (Subtypes 2 and 3):

• When there is no longer a record for the address space (with a given Reader Start Time) the address space has terminated. So the last record for that job name with the given Reader Start Time marks when it came down.
• When there is again a record with the same job name it will have a new Reader Start Time and the address space has come up again.[2]

This is actually a naive implementation but it gets me very close to when an address space comes down.

 

So What?

 

 

The flippant answer is that I extend what my tooling does because it pleases me to. 🙂

 

But actually that’s not true: To the extent that it needs a justification I’m more useful the closer I get to how my customers are running things, and to understanding their problems.

Specifically, in the handful of customers I’ve tested this code with, I have quite a good understanding of the relationship between CICS regions [3] and the batch. For example:

• I see CICS regions come down and not come back up again for hours, sometimes on a timer pop and sometimes event-driven. This is usually overnight and I’m therefore seeing a Batch Window.
• I see CICS regions come down and immediately restarted – in a way that suggests being put into read-only mode or to flip data sets. [4] Again this can be a sign of a batch window.

• I see test regions come up for very short periods of time and then go down again. [5]

Actually, being (supposedly) open minded, I don’t know quite what I’ll see. But these are the sorts of things I think I’ll see.

Here’s a depiction of CICS coming down for Batch and restarting after:

and here’s a conflation of a number of scenarios where CICS gets bounced but is still up alongside batch. In this case it’s in “Read Only” mode:

 

Again, So What?

 

 

The answer to why this might be relevant to you is:

 

• Many of you are looking after a plethoration [6] of systems and applications. This technique might save you time.

• If I start talking to you about up and down times this might help you understand where I got it from. The words “see my blog” escape from my lips quite frequently these days.

And I expect I’ll be updating Life And Times Of An Address Space with this.