To open a VSAM data set, use the Standard C library functions fopen() and freopen() just as you would for opening non-VSAM data sets. The fopen() and freopen() functions are described in z/OS XL C/C++ Runtime Library Reference.
This section describes considerations for using fopen() and freopen() with VSAM files. Remember that a VSAM file must exist and be defined as a VSAM cluster before you call fopen().