Draft Document for Review February 7, 2020 3:15 pm 8464ch02_Architecture.fm GLYPH<SM590000> All virtual volume data within any TS7700 can be auto-expired from TVC cache by using  scratch category delete expire processing. After a volume is moved to a configured  scratch category, any data that is associated with it can be auto-deleted after a defined  grace period passes or the volume is reused during a scratch mount. GLYPH<SM590000> TVC data’s ability to offload to tape or cl oud is managed by definitions in the SC. GLYPH<SM590000> Active data in a stand-alone disk-only TS7700D, the CP0 partition of a TS7700T or  TS7700C, and a DS8000 Object Store partition always remains in the TVC cache. GLYPH<SM590000> In a TS7700T or TS7700C, data in a CPx partition is scheduled to be premigrated to tape  or cloud by using SC policies. Delay premigration policies can be used to defer movement  to tape so that only aged or archive data premigrates to tape. GLYPH<SM590000> If a TS7700T or TS7700C CPx partition runs out of space, the cache management  function removes or migrates previously premigrated volumes from TVC cache. The  volumes that are candidates for removal are chosen based on PG0/PG1 preference  groups. In addition, a TS7700T CPx partition can temporarily overspill into CP0 if CP0  space is available when the CPx partition has no migration candidates remaining. GLYPH<SM590000> In a TS7700T or TS7700C, volumes that are not in TVC cache during a tape volume  mount request are scheduled to be brought back into the disk cache from a physical tape  device or cloud object store by using a recall. The entire volume is recalled into TVC cache  before it is accessible. GLYPH<SM590000> TVC might fill up with large amounts of expired data GLYPH<SM590000> Stacked volumes might retain an excessive amount of expired data GLYPH<SM590000> Stacked volumes fill up with expired data GLYPH<SM590000> Object stores continue to use excessive capacity 2.3.2 Scratched virtual volumes and the Delete Expire function To remain compatible with physical tape, logical volumes that are returned to scratch by your  TMS retain all previously written content until they are reused or written from BOT. In a virtual  tape environment, the indefinite retention of this scratched content can lead to any of the  following situations: To help manage this TMS expired content, the TS7700 supports a function that is referred to  as  delete expire . When enabling delete expire processing against a configured scratch  category, you can set a grace period for expired volumes 1 hour - 2000 years.  If the volume was not reused when the delay period passes, the volume is marked as a  candidate for auto deletion or delete expire. A background process then periodically deletes  candidate volumes. The default behavior is to Delete Expire up to 1000 delete-expire  candidates per hour. This value can be modified by using the  LI REQ  command. After the background handler deletes the volume, the volume’s active space in TVC is freed. If  it was also stacked to one or more physical tapes, that region of physical tape is marked  inactive. If it is contained in an object store, it is then marked for pending deletion where  another background task periodically deletes objects in the cloud. The start timer for delete expire processing is set when the volume is moved to a designated  scratch category that includes an assigned delete expire value. If the scratch category has no  delete expire value that is assigned in the MI, the timer is not set. Setting an initial expire time  in the MI categories window is not retroactive for existing content in scratch. Only volumes  that are returned to scratch from that point forward are candidates for delete expire. Also, a  volume is not a candidate for expire processing until at least 12 hours passes since its last  host access.  40  IBM TS7700 Release 5.0 Guide