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CSKL - CICS Serves, Knowing Legacy (is still making most profit for the organization).

How Nat System switched from APPC over SNA to sockets over TCP/IP for the communication between client

(Windows application) and server (CICS on z/OS), using the IBM-provided CSKL listener transaction by implementing a "child server" process, thereby leveraging its original three-

tiered separation-of-concern approach. Advantages and drawbacks of short-living TCP connections used in this

approach. Set-up and configuration of the CSKL.

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Agenda

• Who am I and where do I come from?

• NatStar is just as dead as the mainframe ;-)

• CICS and TCP/IP

• What did we use it for and how?

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GFI-Adelior

[ THE[ THE ee- PROCESS- PROCESS COMPANY ]COMPANY ]

WELKOM - BIENVENUE - WELCOME

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History

adelior benelux

2006

2006

Java / J2EE

GFI

EMD1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

1998 1999 2000 2001 2002

2002

NAT SYSTEMS (FR)

COGNICASE (CAN)

ADELIOR (FR)

19941993

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Aquisition NAT Systems

Application Engineering Project Development

Withdraw from Europe

Integration into Adelior

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What we do

• Information systems: designing and building, integration and implementation - the whole system life cycle

• Manage large and complex projects• BPM• Technologies: Java, web services, web semantics,

Client/Server...• Infrastructure services: Linux, Microsoft• Business intelligence: BO, Cognos…• Application software solutions: accounting, time

management...

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NatStar Development Environment

InformationInformationModellingModelling

ProcessProcessModellingModelling

GUIGUIBuilderBuilder

RepositoryRepository

AP

IA

PI

NCLNCL

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Separation of concern

Application

uses

Pre

sen

tati

on

S

ervi

ces

Dat

a S

ervi

ces

Ap

plic

atio

n

Ser

vice

s

GU

I Ser

vice

s

DB

MS

Ser

vice

s

Operating System Services

Communication Services

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Generation

• NCL for all Application Objects• Generation of ANSI C code• Specific to target platform• Compilation on required targets

Code

Desktop to Mainframe

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CICS TCP/IP

• Different flavours nowadays

• We use “TCP/IP Socket Interface for CICS”– “Vanilla” TCP socket programming

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Listener

• CSKL - The Concurrent Server

• Child Servers– Take Socket

CICS

Client

CSKL

Child servers

Client

Client

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EBCDIC

• Extended Binary-Coded-Digit Interchange Code

• Code Pages

• Little/Big Endian

• Data Conversion is an issue

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Client application

NSW2COMT

NSW2TCPX

TCP/IP stack

NT

VTAM

TCP/IP stack

DB2

CICS

CSKLDSNC

NSSIPTS2

THINGCOM

Server application library

Libraries Classes

zOS

NSCOM.INI

0 connect1 trancode

2 start tran

3 give socket4 take socket

5 question6 EXEC CICS LINK

7 Things_Register_Library8 Return

9 EXEC CICS RETURN

10 reply11 disconnect

The way to the forum...

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Short-living TCP connections

+ Perfect match for short-living transactions

+ Eliminates effect of user “think-time”

+ Great for automatic fail-over

+ Server is stateless

- Server is stateless

- Overhead of connection set-up

- “TIME_WAIT”

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Set-up & Configuration

• EZAC

• Define resources (mainly the listener)

• Tuning (RTFM!)

• Default values are not too bad

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Some resources

• The listener– CSKL Transaction– EZACIC02 Program

• Configuration– EZAC Transaction

• Operation– EZAO Transaction

• netstat

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Hints & Tips

• Design is ever so important

• Know what to expect both ways

• RTFM!

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The F...ine Manual

• That’s in the Communications Server Bookshelf

z/OS Communications Server

IP CICS Sockets Guide

Version 1 Release 5

Document Number SC31-8807-02

Program Number 5694-A01 and 5655-G52

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Questions

• Questions?

• Comments?

• Remarks?

• Thoughts?

• Considerations?

• Issues?

• Anxieties?