Extended-format sequential data sets, for most purposes, have the same characteristics as sequential data sets. However, records are not necessarily stored in the same format or order as they appear. You can refer to an extended-format data set as a striped data set if its data is interleaved across multiple volumes. This is called sequential data striping.
Large data sets with high I/O activity are the best candidates for striped data sets. Data sets defined as extended-format sequential must be accessed using BSAM or QSAM, and not EXCP or BDAM.