How CICS works?

[Router]

Hi,

My question might sounds rank beginner, however, I'm trying to learn it as professional but in vain. The question is about concepts:

Let's say, I've created a Transaction (TRAN1) and in CICS region I've entered the TRAN1 and press the enter key. What are the tasks and the "objects" will come to play before the actual screen is shown to the user. I read it like, a TASK is created and then it eventually goes to KCP but it's confusing. Can someone please share his/her experience. That will be of great help. Also, do someone know of some document which might show all the "functions goes behind the scene" in a pictorial representation...

Any help in this regards is much appreciated.

[Robert Sample]

A full exposition of what happens is well beyond the scope of any forum. However, briefly what happens is:

• The user keys TRAN1 on a screen and hits enter
  The enter key allows the data on the 3270 to be sent to CICS
  The first four bytes are used as the transaction code (TRAN in this case) -- any remaining bytes are user data
  CICS looks up the transaction code in its tables and verifies that the transaction can be executed. If not, abend
  CICS checks to see if the program referenced in the transcation is valid. If not, abend
  CICS checks to see if the program referenced in the transaction has been loaded from disk yet. If not, it is loaded
  CICS transfers control to the program referenced in the transaction
  The program starts executing

[Router]

Thank you Robert. This gives me enough direction to go ahead.

Regards,

[John Knutson]

The question "How CICS works?" is certainly pretty broad. Robert's reply gave you some insight into 3270 task initiation, but you'll find a lot more interactions covered in these two IBM Redbooks:

• CICS Transaction Server from Start to Finish http://www.redbooks.ibm.com/abstracts/s ... .html?Open
  Architects Guide to CICS on System z http://www.redbooks.ibm.com/abstracts/s ... .html?Open

[Router]

The question "How CICS works?" is certainly pretty broad. Robert's reply gave you some insight into 3270 task initiation, but you'll find a lot more interactions covered in these two IBM Redbooks:

[ul]CICS Transaction Server from Start to Finish http://www.redbooks.ibm.com/abstracts/s ... Architects Guide to CICS on System z http://www.redbooks.ibm.com/abstracts/s ... .html?Open[/ul]

Thanks for the links. Does IBM provide some starting-level learning tutorials for CICS too?

[nicc]

Why not search their website or do a general google for 'cics tutorial'?

[zprogrammer]

Lot of manuals here

http://publibz.boulder.ibm.com/cgi-bin/ ... UBMIT=Find

[Router]

Thanks all for the help. A lot to read there.