HSMS helps optimize usage of high-speed disk storage units by offering the migration function. Particularly in the case of frequently changing applications it makes sense to migrate currently inactive (not required) data from the processing level to a background level; such data can still be addressed via the corresponding catalog entry. Saturation states on public volumes or pubspace limits being reached by user IDs can thus be avoided without compromising file availability.
Whenever the Data Management System (DMS) attempts to access a migrated file, an HSMS request is generated automatically; the file is then recalled to the processing level without user intervention. Migration permits more efficient utilization of expensive high-speed external storages without increasing personnel requirements. Since only those pages are migrated which are actually occupied, storage space is saved at the background level in comparison with the processing level.