Most organizations today are trying to maintain a delicate balance between staying competitive and meeting demanding business needs, while keeping development costs down. To help meet customer demands and protect your investment in CICS legacy applications, IBM continues to enhance CICS Transaction Gateway (CTG), which runs on z/OS, Linux, Linux on System z, AIX, Solaris, HP-UX, and Windows.
This article provides an overview of architectural choices using different CTG topology to integrate CICS and WebSphere Application Server (WAS) on z/OS and distributed platforms, modes of implementation, and J2EE Connection Architecture (JCA) resource adapters. It also examines the tools available for problem determination and monitoring, and new enhancements in CTG V7.1 and V7.2.
To help you determine the best way to access CICS from WAS, this article also covers a new offering in WAS on z/OS V7 called WebSphere Application Server for z/OS Optimized Local Adapters (WOLA). This new method of cross-memory local communications between WAS for z/OS and CICS has bi-directional capability, so you can leverage WAS Enterprise JavaBean (EJB) assets as local services from CICS.
CTG is a set of client and server software components that enable a Java application to invoke services in an attached CICS server. Remote Java clients can call CICS applications using ECI Support and Distribute Program Link (DPL) using COMMAREA or channels and containers (if supported, depending on the CICS and CTG level).
CTG is a widely used J2EE connector for CICS Transaction Server (CICS TS) and, in conjunction with WAS, provides a high-performing, secure, scalable, tightly integrated access method in CICS. CTG is scalable, performs well with minimum overhead, and usually doesn’t require any changes to existing CICS applications. By using CTG, you can expand the value of your existing CICS legacy applications and take advantage of WAS functionality.
CTG provides a range of networking options and a choice of Java and non-Java client programming interfaces. The client application can be a Java application or non-Java application using either C, C++, COBOL, or COM interfaces.
JCA and CTG Topology
Before we delve into CTG topology and available resource adapters, let‘s review JCA, which defines a standard for connecting Java 2 Enterprise Edition (J2EE) to heterogeneous Enterprise Information Systems (EISs) such as CICS. The architecture defines a set of scalable, secure, and transactional mechanisms that enable the integration of EISs with application servers and enterprise applications. WAS, as a proprietary J2EE application server, can be extended to support the resource adapter architecture and is then assured of seamless connectivity to multiple EISs. IBM provides a standard resource adapter with the capability to plug into any application server that supports the connector architecture. The Qualities of Service (QoS) provided by the JCA vary, depending on the topology in use. Figure 1 shows CTG and WAS topology choices.
With topology 1, WAS and CTG are deployed on a distributed platform. Both ECI and External Presentation Interface (EPI) resource adapters can be used in this configuration. To exploit CTG V7, WAS must be at V6.1 or higher.