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See The MSO Configuration File for details on Load Balancing configuration parameters. |
In this section: |
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The preceding figure illustrates the minimum entries that must be present in the MSO Configuration File to implement Load Balancing. It also shows the connectivity methodology used by MSO for CICS, VTAM, and TSO. The APPLGROUP=groupname parameter must be present in all MSO Configuration Files of those MSO regions that are to participate in the same MSO Load Balancing group. This is the minimum entry required to activate MSO Load Balancing. The IBI Subsystem must be active at the time that these MSO regions are started.
MSO Load Balancing configuration parameters do not have to be specified. This works because the IBI Subsystem defaults for Load Balancing group and application are used if set and if not, the default APPLNAME for a service block is its service name (SERVICE=). The user trying to Logon who does not specify APPL(..) picks up the default APPLNAME of the first service block of the MSO region that is initially contacted. If all MSO users intend to run in the same environment, then there is no need to segment the Load Balancing group. APPLNAME then serves no purpose, as all users would be specifying the same application name. This also simplifies the MSO Logon specification for the user and bypasses the requirement in CICS for the installation to supply a parameter list to the CICS MSO transaction when a selection menu is presented to the CICS user.
In the preceding figure, the MSO region, MSO1, is only the primary or initially connected MSO region. Using a single Load Balancing connection region is not required. Any of the MSO regions can be connected to by the user as the initial connection. Dedicating a single region has the advantage of not having to define the other regions to the connection logic. For the TSO user only a single set of communication data sets has to be defined. This is also true for the CICS region and in addition, only one CICS MSO transaction has to be defined. The VTAM user only has to know a single applid to enter on the LOGON command.
The preceding figure illustrates an MSO Load Balancing group that has been segmented into several target sub-groups. All of the MSO regions are in the same Load Balancing group. This is indicated by the APPLGROUP parameter in each MSO configuration file. All four have "MSOPOOL" specified.
It can be advantageous to do this type of segmenting. Frequently there is a need to set up a special environment for a group of users or a particular application. It may be necessary to separate these different environments because of setup conflicts or to reserve certain resources to a group of users or to a particular application.
A user first enters the MSO Load Balancing group by initiating a Logon request to an MSO region that is part of the group. Any of the four MSO regions shown above may be the one that the user initially contacts. The destination or target sub-group of regions is based upon the parameters specified in the Logon request. When that sub-group is determined, an individual MSO region in that sub-group is selected based upon the Load Balancing selection criteria.
The preceding figure has three separate sub-groups an MSO user can Logon to. The following are the different groups and the parameters that determine them. None of the three sub-groups includes all four MSO regions that make up this Load Balancing group.
APPLNAME=ADMIN
MSO1 through MSO3 have ADMIN specified as one of their eligible application names. When the Logon request specifies APPL(ADMIN), these regions are selected for Load Balancing routing.
This sub-group is also selected if the Logon request does not have an application name. Default processing is to inspect the first service block in the initially contacted MSO region. The first application name in the first service block is selected as the default application name. When there are no application names defined to the first service block, the service block name is selected as the default. In this case, ADMIN defaults as the application name.
APPLNAME=PAYROLL
For this sub-group to be selected for Logon routing, APPL(PAYROLL) must be present in the Logon request. There is no way to default to these groups as the default application name for the server block is ADMIN.
APPLNAME=TEST
For this sub-group to be selected for Logon routing, APPL(TEST) must be present in the Logon request when the initially contacted MSO region is not MSO4. When the initially contacted MSO region is MSO4 the default application name is TEST as this is the first (and only) application name specified.
In this example, MSO4 is intended to be used as a maintenance or test MSO region. PRIVATEDD has been set to FIRST so a private set of libraries may be allocated to override the general set.
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