Recommendations for using extended address volumes (EAVs)

  • You can use EAVs as backup, ML1, and ML2 volumes. You can enable allocation of backup, ML1, and ML2 data sets in cylinder-managed space using SETSYS parameter USECYLINDERMANAGEDSPACE. See USECYLINDERMANAGEDSPACE: Specifying whether to allow use of cylinder managed space for migration copies and backup versions.
  • You should evaluate the SMS and non-SMS breakpoint values to limit the over allocation of small data sets in the cylinder-managed space on backup, ML1, and ML2 extended address volumes. Depending on the breakpoint value, over allocation might still occur for large data sets, however, the percent of over allocation is small in comparison to the total disk space request. Small data sets should be allocated in track-managed space and large data sets allocated in cylinder-managed space to limit over allocation. For more information, see the topic about Extended Address Volumes in z/OS DFSMS Using Data Sets.
  • EAVs configured as L0 volumes should not be used as a repository for small data sets. Doing so will negatively impact performance.