8464ch02_Architecture.fm Draft Document for Review February 7, 2020 3:15 pm GLYPH<SM590000> An excess of volume content is moved from one partition to another as part of a policy  change, followed by mount activity or  LIBRARY REQUEST PARTRFSH  activity. GLYPH<SM590000> CPx receives more content during a workload than can be premigrated. This issue might  be because of the CPx partition being smaller than the premigration queue size. Or, it can  be a result of an inability to perform premigration. When either of these conditions occur, it  is referred to as  overspill . In each of these cases, the excess space is taken from CP0’s usable capacity, and the  TS7700T is not viewed as degraded. It is by design that CP0 lends temporary capacity for  these expected use cases. If CP0 has no remaining free space, further overspill is prevented. In addition, a LI REQUEST  tunable is provided to limit how much overspill can occur into CP0. In the following scenarios, a logical volume can be moved from one partition to another: Moving logical volumes between CP partitions GLYPH<SM590000> A virtual volume’s policy changes during a m ount/demount sequence and a new SC rule is  applied. The movement occurs when the volume is closed or unmounted. While mounted,  the volume remains in its originally assigned partition. GLYPH<SM590000> The  LI REQ PARTRFSH  command was run, which enables a partition assignment change to  occur without a mount/demount sequence. When  PARTRFSH  is used, no other construct  changes are refreshed other than the assigned partition. For example, pool properties that  are assigned to the volume during its last mount/demount sequence are retained.  GLYPH<SM590000> Virtual volumes that are still in disk cache are immediately reassigned to the new partition  and the active content value for the source and target partition are automatically adjusted. GLYPH<SM590000> If  PARTRFSH  is used, the last access or creation time is not modified. Therefore, any delay in  premigration continues to be honored if the target partition can accommodate the delay. GLYPH<SM590000> If a mount/demount is used, the last access time is modified. Therefore, any delay in  premigration based on access time is delayed further. GLYPH<SM590000> Any other changes in constructs, such as preference group, premigration delay rules, and  pool attributes, are kept only if the movement is the result of a mount/demount sequence. GLYPH<SM590000> Virtual volumes only in CPx cache and not yet on back-end physical tape are reassigned  to CP0. GLYPH<SM590000> Virtual volumes currently in CPx cache and on tape have the cache copy that is  reassigned to CP0, and all copies on tape invalidated.  GLYPH<SM590000> Virtual volumes that are in CPx and on only physical tape have the partition reassigned,  but a copy is not automatically recalled into CP0 disk cache. If a recall occurs later, the  instance that is recalled into CP0 disk cache becomes the only copy on that cluster. Any  previous physical tape instances are removed from physical tape.  GLYPH<SM590000> Any other changes in constructs, such as removal properties, are kept only if the  movement is the result of a mount/demount sequence. The following rules apply for CPx to CP0 movements: The following rules apply for CPx to CPx movements: In either case, logical volumes can be moved from CP0 to CPx, from CPx to CP0, and from  CPx to a different CPx partition.  If more construct changes are required, such as moving data from one pool to another,  use a mount/demount sequence instead. The command must be issued to a TS7700T  distributed library for each logical volume that must be moved. 22  IBM TS7700 Release 5.0 Guide