In a multiple DFSMShsm-host environment, you must provide protection to prevent control data sets from entering into interlock situations. If you do not have a Global Resource Serialization-like product installed, you must protect your control data sets by ensuring that the following situations/conditions occur:

• That a CDS and the catalog where it is located are on the same volume. If you allocate a CDS on a volume other than the volume containing the catalog, interlock problems can occur.
• That control data sets are not placed on migration level 1 volumes. Placing control data sets on migration level 1 volumes may lead to degraded performance or a lockout in a multiple DFSMShsm-host environment.

  Volumes containing control data sets are subject to reserves in a multiple DFSMShsm-host environment. Migration level 1 volumes are also subject to reserves when small-data-set-packing data sets are accessed.

• That each CDS has a unique high-level qualifier that is cataloged in the user catalog on its respective volume if all control data sets in the catalog cannot reside on the same volume.
• That control data sets are not placed on the same volume with system resource data sets.