For coupling facility log streams, staging data sets are optional. However, Logger allows staging data set attributes to be defined and updated for all log streams, whether or not staging duplexing is requested. Therefore, IBM® recommends that you plan for staging data sets for each system even if your installation does not intend to use them for duplexing and does not define duplexing to staging data sets in the log stream definition. This is recommended because system logger might allocate temporary staging data sets to safeguard log data when there is an error that leaves the only copy of log data in a volatile configuration. Specifically, system logger automatically allocates a staging data set when a structure failure followed by a rebuild failure leaves the only copy of log data for a log stream in local storage buffers. System logger automatically allocates staging data sets for each system not already using them under these conditions, even if you do not specify duplexing to staging data sets. System logger automatically allocates temporary staging data sets during rebuild processing. System logger does the following to allocate staging data sets during rebuild processing:

• Allocates a staging data set on each system.
• Copies the log data into the staging data set.
• Disconnects user connections to the log stream and places the system connection to the log stream into a failed state.