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If different z/OS generic device group search orders (or preference values) have been specified for generic device groups containing CA MIA managed devices on systems in the CA MIM complex, then the potential exists for a cross-system deadlock on generic device groups. Values for generic device group preference are specified in the Hardware Configuration Definition.
Specifying the same z/OS preference order on all the systems defined to the MIMplex prevents this type of lockout. Generic device groups are acquired one at a time, but must all be acquired prior to proceeding into allocation.
For example, imagine that there is a two-system MIMplex, comprised of SYSA and SYSB. SYSA and SYSB preference the generic device groups in reverse order (SYSA preferences in the order 3480, 3490; and SYSB preferences the 3490 generic first followed by the 3480 generic). If an allocation request occurs simultaneously on both systems, then SYSA first acquires generic device group 3480 per its preference order. SYSB acquires 3490 per its preference order. Each system then attempts to acquire the generic device group already acquired by the other system, resulting in a deadlock.
Specifying the same z/OS preferencing order of generic device groups on the EDL prevents this type of lockout from occurring.
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