Beginning in z/OS V2R1, you can specify extended addressability for a VSAM linear data set (LDS) that is neither extended-format nor SMS-managed. This allows the LDS to exceed the four-gigabyte size limit of SMS-managed data sets, and thus able to serve as a zFS version root not subject to the size limits and other restrictions of SMS-management. If you wish to change an existing VSAM LDS, use IDCAMS ALTER with the EXTENDEDADDRESSABLE (EXTADDR) parameter. This will alter an existing non-SMS LDSes to extended addressability. If you want to allocate a new VSAM LDS that is greater than four-gigabytes an non-SMS managed, you can use the IDCAMS DEFINE command with a DATACLASS specification indicating a data class that specifies extended addressability LDSes without extended format. For more information on the data class specification necessary for a non-SMS managed VSAM LDS that exceeds four gigabyte, see Extended Addressability details for VSAM data sets inz/OS DFSMSdfp Storage Administration. For the IDCAMS ALTER command, see z/OS DFSMS Access Method Services Commands.
