Name resolution example

The following diagram shows an example CICSplex consisting of four CICS regions, each executing on separate OS/390® machines within a sysplex.
Figure 1. CICSplex using DNS connection optimization
This diagram shows a cicsplex consisting of 4 CICS regions, each executing on a different OS/390 machine within a sysplex. The systems are named MVS1A, MVS1B, MVS1C and MVS1D, with the CICS regions having APPLIDs of CICSPROD1, CICSPROD2, CICSDEV1 and CICSDEV2. The sysplex is defined to the DNS to have the name PLEX1 and each MVS machine has a single IP address. It shows the names that a client machine could use to access the CICS regions. Thest are all described in the following text.
The MVS systems are named MVS1A, MVS1B, MVS1C and MVS1D, with the CICS regions having APPLIDs of CICSPROD1, CICSPROD2, CICSDEV1 and CICSDEV2
The sysplex is defined to the DNS to have the name PLEX1 and each MVS machine has a single IP address. The above diagram describes the names that a client machine could use to access the CICS regions based on the following resource definitions installed on each CICS:
The names that a client can access are:

You can also address individual CICS regions within a group by using their APPLIDs (or server names). For example, CICSPROD1.WWW.PLEX1.IBM.COM will return the address of MVS1A. This is equivalent to MVS1A.PLEX1.IBM.COM, but the client does not have to know the machine on which the CICSPROD1 server is running, only that CICSPROD1 is part of the WWW group.

Since these names dynamically become available as CICS regions register with the WLM, adding more CICS regions and more MVS machines does not result in any more administration. Using the generic host names (such as WWWDEV.PLEX1.IBM.COM) decouples client applications from specific CICS regions and MVS hosts, which enhances availability and scalability.