Using SSM Global Application › Sharing Resource Status Information

Sharing Resource Status Information

Two or more systems can share resource status information if they have the same SSMPLEXNAME setting. The SSMplex may include the same systems as a SYSplex, or may include a subset or superset of systems in a SYSplex.

Shared data is maintained in the GST (Global Status Table), which is maintained by the global system. Only one global system is active at any time.

Every SSMplex member has an SSMPRIORITY value between 0 and 999 that is used to select the “global” system.

• Priority 0 systems can never be assigned as the global system.
• Priority 1 is the last priority that will be chosen.
• Priority 999 is the first to be chosen.
• Priority 1000 is used to force an eligible alternate global system to become the global system. The system’s normal priority is added to 1000 to create a priority that is higher than any other normal priority. Once the new system becomes the new global system, the priority is reset to the original priority by subtracting 1000.

Priority affects the choice of a new global system when no global system is active, but otherwise has no effect. See the SSMPRIORITY section in this chapter for more information.

Only systems that have a multi-system facility (MSF) connection to every other system in an SSMplex are eligible to be the global system. Eligibility and priority are both taken into account when selecting a new global system.

In normal operation, the global system uses MSF connections to collect status information and also distribute commands to the other systems.

SSMGA data collection is performed asynchronously by multiple subtasks. Using subtasks for data collection:

• Enables SSMGA global processing to continue, using the most recent data available, even if data collection is delayed on one or more systems in the SSMplex.
• Avoids interference with existing SSM processing.