Draft Document for Review February 7  2020 3:15 pm 8464ch02_Architecture.fm The TS7700 with SAA function activated uses policy management with z/OS host software to  direct scratch allocations to specific clusters within a multi-cluster grid. The Management  Class construct determines which clusters should be used for a workload when SAA is  enabled by using the  LI REQ DEVALLOC  command. In a stand-alone environment  the mount is directed to the virtual drives of this cluster. In a  grid environment  specific mounts are more advanced. For more information  see 2.4.12   “Mounting a specific virtual volume” on page 71. In the stand-alone environment  the following scenarios are possible:  2.2.6 Mounting a specific virtual volume GLYPH<SM590000> A valid copy exists in the TVC. In this case  the mount completes quickly and the host can  access the data immediately. GLYPH<SM590000> A valid copy does  not  exist in the TVC. In this case  the following options are available: – If it is a TS7700T  the volume exists in  CP1-CP7 and was copied to physical tape. The  virtual volume also is recalled from a stacked volume. Mount completion is signaled to  the host system only after the entire volume is available in the TVC. – If it is a TS7700C  the volume exists in CP1-CP7 and was copied to an object store.  The virtual volume also is recalled from the cloud tier. Mount completion is signaled to  the host system only after the entire volume is available in the TVC. – Assuming a stand-alone cluster  if no consis tent copy exists in disk cache or within  attached tape or cloud  the mount fails. If in a grid  a peer’s TVC can be chosen as well. Any recalled virtual volume remains in the TVC until it becomes the least recently used (LRU)  volume  unless the volume was assigned a Preference Group of 0 or the  Recalls Preferred to  be Removed from Cache  override is enabled by using the  TS7700 Library Request  command. If a recalled volume is modified  the new instance of the volume is premigrated to tape or  cloud and the previous instance is invalidated. If the recalled volume is not modified  no  premigration occurs unless a pool configuration change occurred as part of the mount.  For example  if the primary or secondary pool changes as part of a mount operation  a  premigration occurs to one or both pools. Any instance in a previous pool is invalidated.  Furthermore  copies to remote TS7700 clusters in a grid configuration are not required if  modifications were not made  unless the Management Class also changed and retain copy  modes is not enabled. Any specific or private mount must target a logical volume that is assigned to a non-scratch  category. The tape management system (TMS) prevents a scratch volume from being  mounted in response to a specific mount request.  Also  the TS7700 treats any specific mount that targets a volume that is assigned to a scratch  category  which is also configured through the MI as scratch. If this process occurs  the  temporary tape header is created  and no recalls take place. The DFSMS Removable Media  Manager (DFSMSrmm) or other TMS likely fail the mount operation because the expected  last written data set for the private volume was not found. Because no write operation occurs   the original volume’s contents  are left intact  which accounts for categories that are incorrectly  configured as scratch within the MI. 34  IBM TS7700 Release 5.0 Guide