MVS™ provides the support that allows the installation to specify through its policy information whether or not a coupling facility structure should be rebuilt when a loss of connectivity to the coupling facility occurs. Loss of connectivity to a coupling facility can occur because of a failure of a coupling facility attachment or because of certain types of failures of the coupling facility itself. Depending on the scope of the failure, the appropriate action for MVS to take might be to initiate rebuild of a structure.

When a loss of connectivity from a system to a coupling facility occurs, MVS detects the failure on one or more systems in the sysplex. Each system on which the loss of connectivity is detected will execute an algorithm to determine what action should be taken. The algorithm is executed for each coupling facility structure affected by the loss of connectivity. Based on the results of the algorithm, MVS determines if policy action should be taken and notifies each connected user of the loss of connectivity event.

To allow MVS to initiate this structure rebuild, the installation must do the following:

1. Have a structure for which all active connections support structure rebuild.
2. Specify a REBUILDPERCENT value in your CFRM policy for each structure that MVS is to evaluate for rebuild, or allow it to default to 1. Note that the default rebuild percent value is 1 for systems at OS/390® Release 10 and higher and for lower-level systems with OW41959 applied. Otherwise, the default rebuild percent value is 100.
3. Optionally, have in place an active SFM policy that supports the use of system weight values for performing recovery actions in the event of loss of connectivity between systems. (An active SFM policy is required for a sysplex made up of systems at OS/390 Release 2 or lower or a sysplex without OW30814 installed, if you want MVS to initiate a structure rebuild.)