VSAM data sets are defined using either access method services commands or JCL dynamic allocation. A summary of defining a VSAM data sets follows:

1. VSAM data sets must be cataloged. If you want to use a new catalog, use access method services commands to create a catalog. The procedure for defining a catalog is described in z/OS DFSMS Managing Catalogs.
2. Define a VSAM data set in a catalog using the TSO ALLOCATE command, the access method services ALLOCATE or DEFINE CLUSTER command, dynamic allocation, or JCL. Before you can define a VSAM data set with dynamic allocation or JCL, SMS must be active on your system. Dynamic allocation and JCL do not support most of the DEFINE options available with access method services.
3. Load the data set with either the access method services REPRO command or your own loading program.
4. Optionally, define any alternate indexes and relate them to the base cluster. Use the access method services DEFINE ALTERNATEINDEX, DEFINE PATH, and BLDINDEX commands to do this.

After any of these steps, you can use the access method services LISTCAT and PRINT commands to verify what has been defined, loaded, or processed. The LISTCAT and PRINT commands are useful for identifying and correcting problems.