The z/OS® UNIX System Services element uses a couple data set to maintain information to support a shared file system in a sysplex. There is no policy associated with the OMVS couple data set, although it must be formatted with the IXCL1DSU format utility. See “Sharing files systems in a sysplex” in z/OS UNIX System Services Planning for information about the z/OS UNIX support for a shared file system. See Planning the couple data sets for considerations that must be reviewed when formatting a couple data set and z/OS UNIX parameters for format utility for the syntax used to format the OMVS couple data set.