The page data set protection feature was introduced in z/OS® V1R3 to help guard you from unintentionally IPLing with a page data set that is already in use. It does this by formatting and maintaining a status information record at the beginning of each page data set and by using an ENQ to serialize usage of the data sets.

The page data set protection feature prevents two systems from accidentally using the same physical data set. However, it is not possible to prevent the same data sets from being used when:

• the request to use the data set comes from a system outside of the GRS Ring/Star configuration.
• the installation has excluded the data sets from multi-system serialization. See z/OS MVS Planning: Global Resource Serialization for more information on SYSTEMS Exclusion RNL.