The CICS® Transaction Gateway includes an External Call Interface (ECI) resource adapter for CICS. The ECI resource adapter provides standard CCI interfaces that enable J2EE components to call CICS server programs, using data areas (COMMAREAs) to pass information to and from the server. Typically, these J2EE components are servlets or enterprise beans; in all cases, they execute outside CICS.
CICS TS includes the CCI Connector for CICS TS, which provides standard CCI interfaces that enable Java programs and components (for example, enterprise beans) running within CICS to call CICS server programs.
The connector uses a JCICS Program.link() call to access the back-end server program. Link and distributed program link (DPL) calls are supported. This scenario is shown in Figure 1. In this example, a Java client application or servlet uses RMI-IIOP to create an instance of an enterprise bean in a CICS EJB server. The enterprise bean uses the CCI Connector for CICS TS to link to a server program on a back-end CICS Transaction Server for z/OS region.
A Java client application or servlet uses RMI-IIOP to create an instance of an enterprise bean, which exists in a CICS EJB container. The enterprise bean uses the CCI Connector for CICS TS to link to a server program on a back-end CICS TS for z/OS region.
To create an enterprise bean that uses the CCI Connector for CICS TS, the Java programmer requires a reasonable knowledge of CICS (although somewhat less than if he or she were using JCICS). However, the enterprise beans that are created can be used by Java programmers who have little knowledge of CICS.
The CCI Connector for CICS TS is highly optimized for execution within CICS; there is very little overhead involved in using it rather than a JCICS Program.link() call.