ISAM Interface Program (IIP)

CMS does not support the VSAM ISAM Interface Program (IIP). Thus, any program that creates and accesses ISAM (indexed sequential access method) data sets cannot access VSAM key sequential data sets.

There is one exception to this restriction. If you have OS PL/I programs that have files declared as ENV(INDEXED) and if the library routines detect that the data set being accessed is a VSAM data set, your programs will execute VSAM I/O requests.