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

Chapter 7. Interactions with the DB2 Family of Products
In this book CICS for AIX is the application server of choice. CICS for AIX
provides the environment in which applications run. Those applications perform
the necessary business logic; that is, the reading and writing of enterprise data.
Data is accessed by applications at a logical rather than a physical level.
CICS for AIX provides access to four different types of data storage facilities:
files services, queue services, relational database services, and journal services
(see 3.1.4, “Access to Data” on page 27). In deciding which of these data
storage facilities to use to store your application data, you must consider the
following major issues: data structure, management functions, recovery of lost
data, data sharing, distribution capabilities, integrity of shared data, and
performance.
The use of an RDBMS is increasingly regarded as the most effective solution
that addresses all of these issues. An RDBMS has knowledge of the logical and
physical structure of the data. The structure information is held separately from
the application. Thus the data structure can be changed significantly without any
need to change the application. An RDBMS provides services and utilities for
managing the recovery, sharing, and distribution of data. This presents a
significant step forward for distributed processing as the inability to share data
has historically been an impediment to application growth and change. Current
hardware and software now make it practical to distribute a single database
among several remote locations. Distribution allows you to keep data local to
the code that most often uses it without restricting access to it by other users.
An RDBMS maintains the integrity of the data under its control.
The integrity of data must be maintained as it is accessed and updated from a
CICS application. Ensuring data integrity requires the use of an interface
between CICS for AIX and any RDBMS in which data is accessed. The interface
must be capable of coping with decisions as to whether to commit updates or
back them out. Such an interface must also be able to cope with the fact that
data has been updated in a location other than the CICS for AIX region or
RDBMS. Ideally the interface should also conform to a standard so that any
RDBMS conforming to the standard can be connected to CICS for AIX. Having
several RDBMSs from which to select gives the enterprise more flexibility in
combining CICS for AIX with the RDBMS of its choice. In order to achieve this
level of data integrity and flexibility, database access is provided through the
X/Open XA interface. The use of the X/Open XA interface requires support in
both CICS for AIX and any RDBMS to which it connects. The X/Open XA
interface is covered in more detail in 7.1, “X/Open XA Interface” on page 86.
At the time of writing the RDBMSs supported by CICS for AIX Version 2.1.1 are
DB2 for AIX V1.1 with appropriate program temporary fixes (PTFs), DB2 for AIX
V2.1, Informix V5.0.5, Oracle V7.1.6, and Oracle V7.2.2. We focus on the DB2
family of products, which is a collective name for IBM RDBMS products available
for the mainframe, Intel-, and UNIX-based platforms.
The DB2 family of products has a very high level of interconnectivity in the same
way that CICS does. The versions of DB2 that run on AIX, OS/2, and Windows
NT belong to the DB2 common server. DB2 common server is the generic name
for DB2 products running on Intel- or UNIX-based platforms. They provide a
common set of functions and connectivity among themselves.
© Copyright IBM Corp. 1996 85