Programs process data sets in the following sequence:

1. Allocate the data set to establish the logical link between a program and a data set. You can do this either outside the program with JCL or the TSO ALLOCATE command or inside the program with dynamic allocation.
2. Open the data set, identifying it with a DDNAME.
3. Do reads and writes using an access method.
4. Close the data set.
5. Deallocate the data set. There are three ways to do this:
   • For non-VSAM data sets only, specifying FREE=CLOSE when closing the data set. (The FREE=CLOSE parameter is ignored for VSAM data sets.)
   • Your program can call dynamic deallocation.
   • During the step termination process, the operating system automatically deallocates any remaining allocated data sets.