CICSPlex® SM makes use of a distributed system management architecture that is based on a manager-and-agent model. In CICSPlex SM, the agent runs in a managed CICS® system, otherwise known as a managed application system (MAS). The agent is in constant communication with a manager, called a CICSPlex SM address space (CMAS). This communication allows the manager to monitor and control the CICS system. The manager consolidates data from, and distributes actions to, the individual agents. The manager is also responsible for basic management applications, such as resource monitoring and workload management.
A typical CICSplex configuration would consist of many agents under the control of a single manager. In a more complex environment, there might be multiple managers, each controlling multiple agents. In order to achieve the distributed system management goal of a single-system image, these managers are normally connected to each other.
Another important aspect of distributed system management
that is provided by CICSPlex SM is operation from a single point of control. In CICSPlex SM,
the single point of control is either:
Providing the single-system image and single point of control is a responsibility shared by many parts of the CICSPlex SM system. An end user, from a TSO session, enters the ISPF interface via the InfoManager. The InfoManager calls on the CAS to locate a CMAS capable of processing the user’s request. The InfoManager then communicates with the target CMAS, using links between CASs, if necessary. So it is the CAS that provides the single point of control by ensuring that the InfoManager is able to communicate with whatever CMAS is needed to perform a given request. But the CMAS distributes the request to multiple CMASs and MASs, as appropriate, and then consolidates the results of the request for presentation to the user via the InfoManager. So it is the CMAS that provides the single-system image by knowing which CMASs and MASs must participate in the processing of a request, routing the request to those destinations, and consolidating the results.
In addition to the visible parts of the CICSPlex SM system that either manifest themselves as MVS address spaces (such as the CAS) or run within existing address spaces (such as the agent code for a managed CICS system, which runs in the CICS address space), there is one largely invisible part of the system that is also an address space: Environment Services System Services (ESSS). An ESSS address space resides in each MVS image where a CMAS is run. The ESSS is automatically created when the first CMAS is started in a given MVS image and it remains for the life of the IPL. The ESSS provides the cross-memory services used for communication between a manager and agents when they reside on the same MVS image. It also serves as the owner of all data spaces used by the product, which enables data spaces that are shared between a CMAS and a MAS to survive the shutdown of either.
Figure 2 illustrates the basic structure of the CICSPlex SM system.
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