The DFSMS statistics and configuration record (type 42, subtype 6) provides information about data set level performance. Each IBM-supplied mountable file system resides in a data set. I/O statistics for those data sets represent I/O statistics for the mountable file system. Each z/OS® file system (zFS) resides in a linear data set. Each hierarchical file system (HFS) resides in an HFS data set.