There are two ways in which files can be defined as eligible for
BWO.
By specifying the BWO option for the data set using access method services
By specifying the BWO option on the CICS® file resource definition in the CSD
Specifying BWO using access method services
If your data sets are accessed in RLS mode, the BWO option must
be defined in the ICF catalog. To define BWO in the ICF catalog, use the BWO
parameter on the access method services DEFINE CLUSTER statement.