All VSAM data sets, which are known as clusters, are defined and maintained using IDCAMS, which provides functions to create, copy, list, delete, and verify VSAM files. For detailed information concerning VSAM and IDCAMS functions, please refer to IBM's VSAM Primer and Reference Manual.
You must use IDCAMS to define the VSAM catalog before processing a VSAM data source. The catalog contains necessary information about the cluster, including its location and physical characteristics.
A database administrator or other authorized individual must allocate the VSAM catalog and grant users the authority to access (and/or update) the VSAM catalog or data sets. With write authority at the data set level, you can issue any IDCAMS command from VM/CMS and OS/390 or MVS.
The IDCAMS DEFINE function is used to describe VSAM attributes and record them in the master catalog. The volume serial number where each cluster resides is also recorded in the catalog at this time. All new VSAM data sets must be defined before you can load them with a MODIFY procedure.
If you declare an alternate index in your FOCUS Master File, you must also use a DEFINE to describe that alternate index and its path.
There are many optional DEFINE parameters. When defining VSAM files to FOCUS, we recommend using the IMBED and NOREPLICATE parameters to reduce access time, and SHAREOPTIONS (2) to ensure data integrity. The SHAREOPTIONS (2) parameter allows only one person to update a file at a time, but many can read it.
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