Probably the definitive place to check is in the "PR/SM Planning Guide". The z13 one is SB10-7162, and the relevant section is "Storage Configurations" -> "Central Storage" where it lists the storage granularity (page 96 in the latest version).
It agrees with the previous answers :-) Geoff Rousell IBM mainframe SE ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
