ISAM refers to two access methods: basic indexed sequential access method (BISAM) and queued indexed sequential access method (QISAM). Data sets processed by ISAM are called indexed sequential data sets. Starting in z/OS V1R7, you cannot create, open, copy, convert, or dump indexed sequential (ISAM) data sets. You can delete or rename them. You can use an earlier release of z/OS to convert them to VSAM data sets.
Important: Do not use ISAM. You should convert all indexed sequential data sets to VSAM data sets. See Using the Indexed Sequential Access Method.