Locating CMASs

Start of changeThe CMAS is the component of the CICSPlex® SM topology that is responsible for most of the work involved in managing and reporting on systems and their resources. It is the CMAS that is responsible for presenting the SSI to the operator. Each CICSplex is managed by at least one CMAS. This section gives you guidance on deciding where to put CMASs and how many to have.End of change

Where to install CMASs

Now that you have decided which CICS® systems are to be managed by CICSPlex SM, and how they are to be organized into CICSplexes, you should think about where CMASs are required. The rules and recommendations governing where a CMAS can, and must, be installed are:

You should also consider the performance implications of your decision. Each CMAS has its space requirements and its own data repository. If you plan to use the ISPF EUI on the image, you will need to install a CAS. For details of estimated space requirements of the CICSPlex SM components, see Planning CICSPlex SM installation and setup.

If we apply these rules and recommendations to the example enterprise, you can see that:

Figure 6 shows the example map updated again, this time to show the application of these CMAS rules and recommendations.

CMAS-to-CMAS links

When a CICSplex crosses multiple MVS images, multiple CMASs are likely to be involved in managing that CICSplex. The CMASs must be connected to each other (using CICS intercommunication methods) so that data relating to the CICS systems belonging to the CICSplex is accessible by all relevant CMASs, and an SSI can be presented to the CICS operator. The minimum requirement is that CMASs managing the same CICSplexes be linked to form an open chain of CMASs, so that each CMAS is linked, if only indirectly, to every other CMAS. Meeting this requirement ensures that there is at least one path from each CMAS to every other CMAS involved in managing the same CICSplex. To achieve the best performance and availability, link every CMAS directly to every other CMAS.

Figure 7 illustrates the concept of direct and indirect CMAS-to-CMAS links.

The links between multiple CMASs involved in managing the same CICSplex are responsible for the SSI of the CICS systems or systems that belong to that CICSplex. However, you do have a degree of choice regarding the number of links you define. First, here’s a reminder of the rules and recommendations concerning CMAS-to-CMAS links:

In the example configuration, full CMAS-to-CMAS connectivity is established for each of the two CICSplexes. That is, for management of CICSplex 1, CMASs 1, 2, and 3 are directly connected to each other; for management of CICSplex 2, CMASs 4 and 5 are directly connected to each other. Thus, eight CMAS-to-CMAS links must be defined:

CICSplex 1 CICSplex 2
CMAS1 to CMAS2 CMAS4 to CMAS5
CMAS1 to CMAS3 CMAS5 to CMAS4
CMAS2 to CMAS1  
CMAS2 to CMAS3  
CMAS3 to CMAS2  
CMAS3 to CMAS1  

You could have decided not to link CMAS 1 to CMAS 3 directly. This arrangement would have met the minimum CMAS-to-CMAS link requirement (by leaving us with an open chain of CMASs) and would have reduced the number of links to be defined by two. Had you done so, information requested from System C about CICS resources on System A, for example, would be obtained indirectly (via the adjacent CMAS, CMAS 2) rather than directly. Wherever full connectivity is not established among a group of CMASs, CICSPlex SM works out the quickest route to the requested data dynamically.

The performance impact is slightly higher when information is obtained indirectly, but this needs to be set against the overhead of setting up and maintaining the CMAS-to-CMAS links. In fact, even if you had defined one CICSplex rather than two in your example, full connectivity among the CMASs would have been feasible. (That is, you would have needed 20 CMAS-to-CMAS links, because the number of links required is n2 - n, where n is the number of CMASs to be connected.) However, if you had ten CMASs managing a single CICSplex, the number of links required would jump to 90; if you had 15 CMASs, the number would be 210. In summary, you have to decide how many direct links you are prepared to define, and where indirect links can be accommodated, always remembering that the minimum requirement is for an open chain of CMAS-to-CMAS links.

Figure 8 shows the CMAS-to-CMAS links in the example configuration.

When there are multiple CMASs on the same MVS system, managing the same CICSplex, a local MAS that specifies only the CICSPLEX(name) CICSPlex SM system parameter, and not the CMASSYSID(name) CICSPlex SM system parameter, will connect to the last CMAS to initialize on the MVS image that manages the named CICSplex for a specific release of CICSPlex SM. See the CICS Transaction Server for z/OS Installation Guide for a description of CICSPlex SM system parameters.

CMAS-to-CMAS links for multiple CICSplexes

In our example, there are two CICSplexes. So that the CICSPlex SM operator can access CICSplex 2 data from System B, for example, you could establish a link between any one (or more) of the CMASs involved in managing CICSplex 1 and any one (or more) of the CMASs involved in managing CICSplex 2. For example, you could establish a link from CMAS 1 to CMAS 5, thereby forming a chain of all of the enterprise CMASs.

Alternatively, data belonging to one CICSplex can be accessed from an MVS image on which a second CICSplex resides via CAS-to-CAS links. With the configuration you have chosen, CICSPlex SM information about an AOR on System E, for example, requested from the CICSPlex SM user interface on System A, can be obtained via CAS-to-CAS links rather than CMAS-to-CMAS links. CAS-to-CAS links are discussed in CAS-to-CAS links.

Locating the maintenance point CMAS

When a single CICSplex is managed by multiple CMASs, one of them is designated the maintenance point CMAS. The maintenance point CMAS is responsible for maintaining all CICSPlex SM definitions relating to a CICSplex, and for distributing up-to-date information to the other CMASs involved in managing the same CICSplex, so that no data repository is out of step with any other.

The maintenance point CMAS is the CMAS that is the context value when the CICSplex is defined to CICSPlex SM. (The context is described in topic Display formats.) Each CICSplex can have only one maintenance point CMAS, but a single CMAS can be the maintenance point for more than one CICSplex. If the maintenance point CMAS is unavailable at any time, changes to all CICSPlex SM functions except BAS can be made at another CMAS managing the CICSplex. This CMAS becomes the temporary maintenance point CMAS. Any changes are temporary.

BAS does not support temporary maintenance point CMASs. The maintenance point CMAS must be available if you are creating or maintaining BAS definitions.

Figure 8. Adding CMAS-to-CMAS links to the example map. Eight links have been defined, giving full connectivity among CMASs managing the same CICSplexes.
The map shows the following systems: System A is an OS/390 2.10 system with a CICS Transaction Server for OS/390, Version 1 Release 3 TOR and two CICS Transaction Server for OS/390, Version 1 Release 3 AORs. System B is an OS/390 2.10 system with a CICS Transaction Server for OS/390, Version 1 Release 3 TOR, a CICS Transaction Server for OS/390, Version 1 Release 3 AOR and a CICS Transaction Server for OS/390, Version 1 Release 3 FOR. System C is a z/OS 1.4 system with two CICS Transaction Server for OS/390 Release 2.3 AORs. System D is an OS/400 3.1 system with two CICS/400 3.1 regions. System E is an OS/390 version 2 release 10 system with two CICS Transaction Server for OS/390 Release 2.2 AORs and a CICS Transaction Server for OS/390 Release 1.3 AOR. System G is a z/OS 1.2 system with two CICS Transaction Server for z/OS, Version 2 Release 3 AORs. The CICS regions from System A, System B and System C belong to CICSplex 1. The CICS regions from System E, and System G belong to CICSplex 2. The CICS regions from System D do not form part of a CICSplex. CMAS 1 is installed on System A. CMAS 2 is installed on system B. CMAS 3 is installed on System C. CMAS 4 is installed on system E. CMAS 5 is installed on System F. CMAS 3 and CMAS 5 are both maintenance point CMASs. CMAS 3 also has access to NetView. CICSplex 1 has direct bi-directional links between CMAS1 and CMAS2 and CMAS2 and CMAS3 and an indirect bi-directional link between CMAS1 and CMAS3. CICSplex 2 has an indirect bi-directional link between CMAS4 and CMAS5.

A maintenance point CMAS can also function as a normal (not maintenance point) CMAS for other CICSplexes.

Note:
CICSPlex SM’s single point of control means that changes to the maintenance point CMAS can be made from any system on which the CICSPlex SM EUI is available.
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