The GDGLOCATE statement controls whether the PowerExchange Listener uses the most recent z/OS catalog information to determine the latest generation in a generation data group (GDG) based on a relative generation number when reading or writing generations in a GDG.
NETPORT, TAPEWAIT, and WAITDSN
. The PowerExchange Listener uses the most recent z/OS catalog information for a generation data set when reading or writing a generation data set in a GDG based on a relative generation number.
PowerExchange refreshes the generation table for a GDG by specifying the S99GDGNT bit in S99FLAGS1 on a dynamic allocation (SVC99) request. The dynamic allocation request then uses the LOCATE function to determine the latest absolute generation in the GDG based on the catalog information.
. The PowerExchange Listener does not refresh the generation table with the latest information from the z/OS catalog after it references the GDG the first time by using a relative generation number. All future Listener requests that use the relative generation number will access the same absolute generation as the first reference.
Default is Y.
Assume that you set GDGLOCATE to N, and the relative generation number of 0 for MY.GDG corresponds to the MY.GDG.G0011V00 data set. The first time you reference relative generation number 0 through the PowerExchange Listener, the Listener reads the absolute generation G0011V00. If you create a new generation that has an absolute generation number of G0012V00 and request relative generation 0 through the same PowerExchange Listener, the Listener still reads the absolute generation G0011V00. However, if you use the default setting of GDGLOCATE=Y and request relative generation 0, the Listener uses the latest z/OS catalog information to read the absolute generation G0012V00.