There are instances when the system will automatically contract a structure when the coupling facility as a whole is at or above 90% full and coupling facility resources are not being used productively by the structure. This processing will potentially initiate alter processing against many structures, reclaiming a small amount of storage from each of them, until the coupling facility storage constraint has been relieved.

The structure must have been defined to be eligible for automatic alter (seeAllowing a structure to be altered automatically for the list of eligibility requirements). When structure full monitoring determines that all monitored objects for a particular structure are below the structure full threshold value, the system will start an alter request against the structure to contract the structure. The objective of the alter request is to contract 10 percent of the currently allocated structure size for each eligible structure at any one time. The alter processing will not allow the structure to be contracted below the MINSIZE value specified in the active CFRM policy.