IBM OS manual Introducing transaction affinities

Chapter 1. Introducing transaction affinities

This chapter provides a brief introduction to the concept of transaction affinities and

the associated CICS programming techniques, and highlights the signi®cance of

transaction affinities in a dynamic routing (known in previous releases of CICS as

dynamic transaction routing) environment. For more information about transaction

affinities, see the CICS Application Programming Guide.

This chapter introduces the following topics:

vªThe bene®ts of dynamic routingº on page 3

vªTransaction affinitiesº on page 3

vªCICS programming techniques for transaction affinityº on page 5

vªAvoiding the effects of transaction affinityº on page 6

vªProtecting applications from one anotherº on page 7

CICS has been handling customers' online transaction processing requirements for over thirty years. In that time, it has been extensively enhanced to meet the ever-growing needs of business applications, and to exploit the capabilities of modern computer processors and communication systems. One of the most

signi®cant enhancements in recent times is the addition of the dynamic routing facility.

Originally, a full-function CICS ran in a single address space (region) within the MVS environment. Currently, most CICS users use some form of intercommunications to operate multiple, interconnected, CICS regions (a CICSplex). Using the CICS multiregion operation (MRO) facility, a CICSplex typically consists of one or more terminal-owning regions (TOR), and a number of application-owning regions to which the TORs route the incoming transactions for processing. The CICSPlex SM element of CICS Transaction Server for OS/390 Release 3 includes a workload management component that optimizes processor capacity by dynamically routing transactions to whichever CICS region is the most appropriate at the time, taking into account any transaction affinities that exist. For an introduction to CICSPlex SM, see CICSPlex SM Concepts and Planning; for information about CICSPlex SM workload management, see CICSPlex SM Managing Workloads.

CICS A

Terminal-Owning

Region (TOR)

End-user		MRO
terminal	CICS Relay
	Transaction	links

Figure 1. The CICS transaction routing facility

CICS B

Application-Owning

Region (AOR)

User

Transaction

Before CICS Transaction Server for OS/390 Release 3, TORs routed transactions to the AORs prede®ned in transaction resource de®nitions by the system programmer. This static form of transaction routing adds to the system administration burden of the system programmer, because when transaction workloads have to be rebalanced across the AORs, transaction resource de®nitions have to be modi®ed accordingly.

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