8464ch02_Architecture.fm Draft Document for Review February 7, 2020 3:15 pm Physical pooling of stacked volumes is identified through pool numbers, as shown in  Figure 2-5.  Figure 2-5 TS7700T Logical volume allocation to specific physical volume pool flow DC SC MC SG File Seq 1 Allocation Storage Group = ACS  Routines QRS456 XYZ999 ABC123 V10000 Pool 12 Physical Pool Storage Group 8 12 20 GENVTS USER1 TEST1 TEST2 TEST3 ABC123 Tape Volume  Cache Application Data TS7700 Virtualization Engine Volser Selected =  USER1 ABC123 TS7700 DB VOLSER SG ABC123 USER1 SC - - - - - - - - MC DC - - - - - - - - - - - - - - - - Assignment at volume  Rewind/Unload Through the MI, you assign which primary pool is used for a workload within the SG  attributes. During a scratch mount, a logical volume is assigned to a selected SG and the  assigned pool for that SG is targeted. In addition, MC can be used to define a secondary pool  when two copies on physical tape are required. Physical VOLSER ranges can be defined to target a specific home pool at insert time.  Changing the home pool of a range has no effect on volumes that are in the library. For pools  with borrow/return enabled, target the common pool 00. For pools where borrow/return is  disabled, set up the range table to include volumes that specifically target that pool. Each pool  that contains any amount of active data must always have at least two scratch stacked  physical volumes to prevent low scratch warnings. Tip:  Primary Pool 01 is the default private pool for TS7700T stacked volumes. Borrow and return: Physical Scratch Management  By using the concept of borrowing and returning, physical scratch distribution can be  automatically addressed. With borrowing, stacked volumes can move from pool to pool based on each pool’s assigned  media type and media needs. When all borrow/return enabled pools with active data contain  at least two scratch stacked volumes, any excess physical scratch is returned to the common  pool 00. You need at least two empty stacked volumes in pool 00 and any pool that contains  active data. If borrow/return is not enabled for a specific pool, you must manage its scratch by  using the physical VOLSER ranges and inserting more tapes when counts go below three. One physical pool with an out-of-stacked volume condition results in an out-of-stacked  volume condition to the entire TS7700T cluster. Therefore, it is necessary to monitor all active  pools. Note:  Pools that feature borrow/return enabled and contain no active data eventually  return all scratch volumes to the common scratch pool after 48 - 72 hours of inactivity. 50  IBM TS7700 Release 5.0 Guide