Overview of the User Control exit

In gathering information about a data set, Data Optimizer checks for the User Control exit before checking the data policy. When an OPEN request occurs, Data Optimizer must determine which data sets should be processed by the Data Optimizer Performance component. Typically, these decisions can be made by using the data policy entries combined with the data set’s attributes and the type of processing that is being performed by the accessing program. However, at times you might want to implement selection algorithms that are too complex for the data policy definition. An example would be if you wanted to include jobs that have job names whose fifth character position is a numeric between two and five. Because the source of decision-related information is virtually unlimited, you can create a User Control exit to assist in tailoring Data Optimizer processing to the installation requirements of your site.