Addressing OLTP Solutions with CICS: The Transaction Server ... - Ibm

10.8 Summary
154 CICS for AIX as the Transaction Server
CICS user files (files defined within the File Definitions (FD) stanza) can be
managed on either a DB2 Version 2 (CICS for AIX only) database or an Encina
SFS. Either file manager can permit data to be shared between two or more
regions and between regions and non-CICS applications such as batch
processing programs.
When designing systems to exploit these facilities, you will have to consider the
networking costs of transferring data between the file manager and its client,
and the benefits of distributing the processing and disk access load between
several machines.
CICS attempts to minimize network traffic by avoiding unnecessary interactions
with the file manager. For example, at the end of a transaction CICS will retain
an SFS open file descriptor for possible reuse where a region uses SFS for file
access services. Such open file descriptors are released when the file is closed,
either by an explicit EXEC CICS SET FILE CLOSED request or when CICS is shut
down.
In developing applications for a CICS environment it is important that you
understand the facilities that are available and the way in which CICS processes
work so that you can work with the CICS architecture and not against it. In this
chapter we discuss the key issues that you have to consider.
There are multiple ways in which to code applications. The style most suitable
for your applications will depend on what those applications will do. CICS
provides tools to assist in the development and debugging of applications.
Those applications can be written in multiple languages.
The availability of the CICS ECI and EPI programming interfaces greatly
improves your ability to extend client-server systems. You are no longer bound
by the constraints of a 3270 data stream and BMS maps. GUIs as a front end to
a CICS client are now possible, providing a very modern user interface.