GDG environments

• The GDG base of the currently allocated IEFRDER or IEFRDER2 in the JCL (the current log data set) is the same as the GDG base in the dynamic allocation skeleton.
• The GDG base of the current log data set is different than the GDG base in the dynamic allocation skeleton, or the current log data set is not a GDG.

BCF needs to allocate new log data sets at the following times:

• When the application has abended and you must perform log recovery or batch backout
• During restart for a job step that was canceled
• During restart for a job step after a system failure

For the first case, BCF allocates new log data sets as needed and executes log recovery, if necessary, and batch backout. As the appropriate recovery actions take place, BCF creates at least one, and possibly two, new generations of the GDG data set.

During restart after a failure or job cancel, BCF may be required to perform log recovery and batch backout. If both operations are performed, BCF creates two new GDG data sets before the execution of your application.

The following sections provide details on the planning and preparation you must do to use GDGs in each environment.