Draft Document for Review February 7, 2020 3:15 pm 8464ch02_Architecture.fm Temporary removal threshold This process is used in a TS7700 Tape Virtualization multi-cluster grid where automatic  removal is enabled and a service outage is expected. Because automatic removal requires  validation that one or more copies exist elsewhere within the grid, a cluster outage can  prevent a successful check that leads to disk cache full conditions.  A temporary removal threshold is used to free enough cache space of the TS7700 CP0 cache  in advance so that it does not fill up while another TS7700 cluster is in service. This  temporary threshold is typically used when plans are made to take down one TS7700 cluster  for a considerable amount of time.  The process is run on the TS7700 MI. In addition, the temporary removal threshold can also be used to free up space before a DR  test with FlashCopy. During the DR test, no autoremoval or delete expire process is allowed.  Therefore, use the temporary removal threshold to ensure that enough free space for the  usual productions and the extra flash copies are available in the clusters in the DR family.  The TVC management processes are the same as for stand-alone clusters. In addition to  premigration management and free-space management, the following processes are  available:  This process applies to only a multi-cluster grid configuration in which one or more  TS7700T/TS7700C clusters exist. TS7700T and TS7700C clusters retain data in disk  cache longer than needed if it believes no other peers require a copy. The goal is to  reduce recalls for copy.  After the volume is copied to the required peers, the volume is no longer held in disk cache  for this purpose alone and honors its PG0 or PG1 LRU algorithm. If the copies target a  remote cluster family, the target family retains the data on behalf of its family peers and the  original source cluster is view it as completed.  This process is done to avoid a possible recall operation from being started by remote  clusters in the grid. Only when replication target clusters are known to be unavailable, or  when the amount of retained data to be copied becomes excessive, is this retained data  migrated ahead of the copy process, which might lead to a future recall to complete the  copy. This process is also called  copy throttling .  2.4.24 TVC management processes in a multi-cluster grid GLYPH<SM590000> Copy Data Residency Retention (TS7700T/TS7700C CP1 - CP7) GLYPH<SM590000> RUN Copy Throttling This process applies to multi-cluster grid configurations where the RUN Copy Consistency  Point is used. When enabled, it limits the host input rate if it believes the RUN copies  cannot keep up otherwise. It is intended to prevent any RUN copies from exceeding the  missing-interrupt handler (MIH) timeout value for host jobs. If limiting the host input does not help, the job changes to Immediate/RUN Deferred mode  and an alert is posted to the host console that the TS7700 entered the Immediate-deferred  state. You can modify this setting through the Host Console Request function to customize  the level of throttling that is applied to the host input when this condition is detected. In  some cases, the RUN Copy throttling can be disabled if high bandwidth and minimal  latency between peers exists. Because Synchronous mode copy is treated as Host I/O to  the remote cluster, RUN throttling is not applicable to Synchronous copies. 82  IBM TS7700 Release 5.0 Guide