Draft Document for Review February 7, 2020 3:15 pm 8464ch02_Architecture.fm Assume that you have three different disk partitions and a unique SC for each one. The  following SC definitions are available: GLYPH<SM590000> CP1: Delay premigration 12 hours after volume creation GLYPH<SM590000> CP2: Delay premigration 6 hours after volume creation GLYPH<SM590000> CP3: Delay premigration 3 hours after volume creation In CP1 at 22:00, 6 TB are written every night. The 12-hour delay ensures that they are  premigrated later in the day when less host activity occurs. To make the example simpler, we  assume that no compression exists for all data. In CP2 at 04:00, 2 TB are written. The six-hour delay makes them eligible for premigration at  10:00 in the morning. In CP3 at 07:00, 1 TB is written. The three-hour delay makes them eligible for premigration at  the same time as the other two workloads. Therefore, all 9 TB of the workload begins to meet its delay criteria at roughly the same time,  which produces a large increase in premigration activity. If the premigration queue size is not  large enough, real-time workloads into the TS7700T might be throttled until the premigration  process can reduce the premigration queue size. Ensure that the number of FC 5274 and  FC 5279 features are sufficient or plan the delay times so that they do not all expire at the  same time or when zero to minimal host activity occurs. 2.3.5 Removing or Migrating CPx content  After a volume that is contained within a CPx partition is premigrated to tape or cloud, you can  determine when the CPx copy that remains is flushed/removed/migrated from TVC cache.  This process is accomplished by assigning a preference group within the SC construct that is  defined in the MI. The following SC preference choices are available: Use IART Volumes are removed according to the IBM TS7700s Initial Access Response  Time (IART) assigned by the host during the volume’s creation. The result is  either Level 0 or Level 1. Level 0  Volumes are removed from the TVC when they are copied to tape or cloud. This  concept is called Preference Group 0 (PG0). This control is suitable for data that  is unlikely to be read again because a recall always is required when accessed. Level 1 Copied volumes remain in the TVC until more space is required for a specific CPx  partition and then volumes in that partition are removed from disk cache in a least  recently used order. Before any Level 1 volumes are removed from the CPx  partition, volumes in scratch that are also in the same CPx partition are removed  first. Next, any premigrated Level 0 volumes in the same CPx partition are  removed. Only if space is still needed are Level 1 volumes then removed based  on LRU against other volumes in the same CPx partition. In a z/OS environment, the SC name that is assigned to a volume in the ACS routine is  directly passed to the TS7700 and mapped to the predefined constructs. If the TS7700 has  no matching SC, the SC is auto-created by using the currently defined default SC. For environments that are not z/OS (SMS) environments, the MI can be used to predefine an  SC to a range of volumes when they were initially inserted. The MI can also be used to assign  an SC to a range of volumes that were inserted. 44  IBM TS7700 Release 5.0 Guide