PDSEs are designed to be shared within a sysplex. When choosing volumes for PDSEs in a sysplex, be sure to follow these rules:

• The volume serials for volumes that contain PDSEs must be unique within a sysplex.
• A volume that contains PDSEs must not be open from more than one GRS complex at a time.
• If PDSE extended sharing is active, a volume that contains a PDSE cannot be accessed from more than one sysplex at a time.

In this context, a sysplex is all systems that can connect in a single XCF group, and a GRS complex is all the systems in a GRS configuration. A sysplex never spans more than one GRS complex. Note: for extended sharing, a PDSE can only be shared by the members of a GRS complex that are also members of the same sysplex. For example: in a six-system GRS complex, with four of the systems within the sysplex and two which are not, PDSEs can have extended sharing between the four members of the sysplex, but not the other two, non-sysplex systems. See z/OS MVS Planning: Global Resource Serialization for more information about the configurations that make up a GRS complex.