Unless the CFRM policy specifies that the order of coupling facility in the preference list is to be enforced (ENFORCEORDER(YES)), MVS™ uses the following method of choosing a coupling facility in which to allocate a structure. The system finds the coupling facility identified in the preference list to which the system is connected that best meets the allocation criteria, listed in order of relative importance from most important to least important:

1. For CONNECTIVITY=BESTGLOBAL, coupling facility SFM weight. For a structure without any active connectors, the SFM weight of each coupling facility is the sum of the SFM weights of all systems connected to that coupling facility. For a structure with active connectors, only systems with active connectors are used to determine the SFM weight of the coupling facility. Note that all systems are considered to have equal SFM weight if no SFM policy is active.
2. Connector connectivity to the coupling facility. Note that this only applies to allocation for user-managed rebuild processing that is started with LESSCONNACTION=CONTINUE and causes allocation with CONNECTIVITY=DEFAULT. Otherwise, connector connectivity to the coupling facility is required or already factored into the CONNECTIVITIY=BESTGLOBAL SFM weight criteria.
3. Has a coupling facility operational level (CFLEVEL) equal to or greater than the requested CFLEVEL.
4. If this is a duplexing rebuild connect, is isolated from the coupling facility that contains the old structure instance
5. Has space available that is greater than or equal to the requested structure size (or has the greatest amount of free space available if any coupling facility does not have enough space for the requested structure size).
6. Meets the volatility requirement requested. If volatility was requested, is failure isolated from all connectors to the structure.
7. Is a stand-alone coupling facility and therefore failure isolated from all MVS systems
8. Meets the failure-independence requirement requested by the connector.
9. Does not contain an instance of a structure in the exclusion list of this structure or, if no such coupling facilities exist, does not contain a simplex structure from the exclusion list of this structure.
10. If system-managed duplexing rebuild is a possibility for this structure, is connected to a remote coupling facility that is also in the PREFLIST.
11. For CONNECTIVITY=DEFAULT, has a higher SFM weight than other coupling facilities with equal criteria.
12. Is located higher on the structure’s preference list in the CFRM policy.

If there is no coupling facility in the preference list that meets all these criteria, then the system determines the coupling facility that most closely meets the criteria. To do this, the system uses a weighting system for each of the coupling facilities in the structure's preference list. The weights correspond to the list of criteria — with system connectivity having the highest weight, CFLEVEL the next higher weight, and so on down the list.

Once it has ordered the coupling facilities in accordance with the relative importance of the allocation criteria, the system then attempts to allocate the structure in the coupling facility with the highest weight. If two or more coupling facilities are assigned identical weights, then the selection is made based on the order in which the coupling facilities are defined in the CFRM policy preference list. If the attempt to allocate the structure is not successful, the system attempts structure allocation in successively lower-weighted coupling facilities until allocation is successful. The system will choose the coupling facility that most closely meets the requirements of the connect request.

Depending on the coupling facility selected, once the structure is successfully allocated, the structure attributes might not be as requested.

Messages IXC574I, IXC347I, and IXL015I provide an indication of the allocation criteria used to sort the preference list.