Working with VSAM data sets under z/OS and z/OS UNIX

Be aware of special coding considerations for VSAM files under z/OS® and z/OS UNIX for access method services (IDCAMS) commands, environment variables, and JCL.

A VSAM file is available if all of the following conditions are true:
  • You define it using access method services.
  • You define it for your program by providing a DD statement, an environment variable, or an ALLOCATE command.
  • It has previously contained a record.

A VSAM file is unavailable if it has never contained a record, even if you have defined the file.

You always get a return code of zero on completion of the OPEN statement for a VSAM sequential file.

Use the access method services REPRO command to empty a file. Deleting records in this manner resets the high-use relative byte address (RBA) of the file to zero. The file is effectively empty and appears to COBOL as if it never contained a record.