Draft Document for Review February 7, 2020 3:15 pm 8464ch04_Planning.fm Automatic removal is temporarily disabled while disaster recovery write protect is enabled  on a disk-only cluster so that a DR test can access all production host-written volumes.  When the write protect state is lifted, automatic removal returns to normal operation. This state occurs when less than 3 TB of free space is available that is left in the cache.  After the cache passes this threshold and enters the limited-free-cache-space-warning  state, write operations can use only an extra 2 TB before the out-of-cache-resources state  is encountered. When a TS7700D enters the limited-free-cache-space-warning state, it  remains in this state until the amount of free space in the cache exceeds 3.5 TB.  The following messages can be displayed on the MI during the  limited-free-cache-space-warning state: For more information about these messages, see IBM Knowledge Center. Clarification:  Host writes to the TS7700 and inbound copies continue during this state. This state occurs when less than 1 TB of free space is left in the cache. After the cache  passes this threshold and enters the out-of-cache-resources state, it remains in this state  until the amount of free space in the cache exceeds 3.5 TB. When a TS7700D is in the  out-of-cache-resources state, volumes on that cluster become read-only and one or more  out-of-cache-resources messages are displayed on the MI. The following messages can  display: For more information about these messages, see IBM Knowledge Center. GLYPH<SM590000> Limited free cache space warning – HYDME0996W – HYDME1200W GLYPH<SM590000> Out-of-cache resources – HYDME0997W – HYDME1133W – HYDME1201W Clarification:  New host allocations do not choose a TS7700D Cluster in this state as a  valid tape volume cache candidate. New host allocations that are issued to a TS7700D  Cluster in this state choose a remote tape volume cache instead. If all valid clusters are  in this state or cannot accept mounts, the host allocations fail.  Read mounts can choose the TS7700D Cluster in this state, but modify and write  operations fail. Copies inbound to this cluster are queued as deferred until the cluster  exits this state. The start and stop thresholds for each of the active cache capacity states that are defined are  listed in Table 4-13. State Enter state  (free space  available) Exit state (free  space available) Host message displayed Automatic removal < 4 TB > 4.5 TB CBR3750I  when automatic removal  begins Table 4-13 Active cache capacity state thresholds 162  IBM TS7700 Release 5.0 Guide