Once you have decided where to install CMASs and how to link them, you can turn your attention to the CASs.
The rules and recommendations on where to locate a CAS are:
It’s very easy to update the example map by applying these
rules: there are five CMASs, so there must be five CASs, one on each of the
MVS images on which a CMAS is installed. Figure 10 shows the
addition of the CASs..
If you define no CAS-to-CAS links, the CICSPlex SM operator can sign on to CICSPlex SM via CAS 1 (or CAS 2, or CAS 3) and still have a complete view of the CICS systems and resources in CICSplex 1 because the CMASs managing CICSplex 1 are linked to each other. The same observation is true of CICSplex 2. For example, a CICSPlex SM operator accessing CICSPlex SM via CAS 5 can see data for TOR 3 via the links between CMAS 4 and CMAS 5. However, for both performance and availability reasons, it is better to establish links between CASs also.
A second consideration in the example is the availability of a single point of control for the enterprise. If you add no CAS-to-CAS links, a CICSPlex SM operator cannot see CICSPlex SM data for CICSplex 2 from MVS image 3, for example. This arrangement might be suitable in some enterprises (indeed, it might be the reason why it was decided to have multiple CICSplexes in the first place). However, if you do want a single point of control for the enterprise and have multiple CICSplexes, CAS-to-CAS links are required.
Thus, CAS-to-CAS links can provide a single point of control for the enterprise by allowing the CICSPlex SM operator access to CMASs that may not be even indirectly connected to each other; CMAS-to-CMAS links provide an SSI for all MASs that connect to those CMASs; and CICSPlex SM exploits a combination of CAS-to-CAS links and CMAS-to-CMAS links to give the best possible performance.
In the example, few CAS-to-CAS links are essential. If you add two links, one from CAS 1 to CAS 4, and one from CAS 4 to CAS 1, both CAS 1 and CAS 4 can function as an single point of control because each has access to data about CICSplexes 1 and 2. However, for maximum performance and availability, and because the total number of CASs in the enterprise is small, you are going to link every CAS to every other CAS. As with the CMAS-to-CMAS links, the formula for calculating the number of links to be defined is n2 - n, where n is the number of CASs. In the example, there are five CASs, and so 20 links must be defined to establish full connectivity for the enterprise. If you have room on your map, add the CAS-to-CAS links. As the example map is beginning to look crowded, the CAS-to-CAS links are listed separately in Table 2.
CAS 1 to: | CAS 2 to: | CAS 3 to: | CAS 4 to: | CAS 5 to: |
---|---|---|---|---|
CAS2 | CAS1 | CAS1 | CAS1 | CAS1 |
CAS3 | CAS3 | CAS2 | CAS2 | CAS2 |
CAS4 | CAS4 | CAS4 | CAS3 | CAS3 |
CAS5 | CAS5 | CAS5 | CAS5 | CAS4 |
Full connectivity among the enterprise CASs is recommended for performance and availability reasons. However, it is not essential: if the enterprise CMASs are adequately connected to each other, a single point of control for the enterprise can be established without full connectivity among the CASs.
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