## Stacked volume pool properties 

Logical volume pooling supports cartridge type selection. This selection can be used to create separate pools of 3592 tape cartridges with various capacities of 128 GB - 10 TB, depending upon the type of media and tape drive technology that is used. 

Lower capacity JJ, JK, or JL cartridges can be designated to a pool to provide consistently faster access to application data, such as hierarchical storage management (HSM) or Content Manager. Higher capacity JA, JB, JC, or JD cartridges that are assigned to a pool can address archival requirements, such as full volume dumps. 

## 2.3.12 Logical and stacked volume management 

Whenever a logical volume is created or modified, any data from a previous use of this logical volume that is on a stacked volume becomes obsolete. The new or modified virtual volume is placed in the cache and written to a new location on a stacked volume in the appropriate pool. The previous copy on a stacked volume is invalidated but it still uses up space on the physical tape. Auto deleting expired scratched volumes or ejected volumes can also result in the creation of inactive space on physical tapes. This inactive space can be reclaimed by using reclamation. 

## Physical volume reclamation 

The reclamation process periodically checks for active volume usage percentages for each full stacked cartridge within each pool. As data is removed or expired, the active data value decreases. When it drops below an optional threshold, reclamation occurs, which allows all active data that remains to be copied to new physical stacked tapes. The now emptied tape is returned to a scratch status. 

The data that is associated with a logical volume is considered invalidated if any of the following conditions are true: 

GLYPH<SM590000> A host assigned the logical volume to a scratch category. Later, the volume is selected for a scratch mount and data is written to the volume. The older version of the volume is now invalid. 

GLYPH<SM590000> A host assigned the logical volume to a scratch category. The category features a nonzero delete-expired data parameter value. The parameter value was exceeded and the TS7700T deleted the logical volume. 

GLYPH<SM590000> A host modified the contents of the volume. This modification can be a complete rewrite of the volume or an append to it. The new version of the logical volume is premigrated to a separate physical location and the older version is invalidated. 

GLYPH<SM590000> The logical volume is ejected, in which case the version on physical tape is invalidated. 

GLYPH<SM590000> The pool properties change during a mount/demount sequence and a new pool is chosen. 

The TS7700T tracks the amount of active data on a physical volume in increments of 0.1% and always rounds up. During a premigration or reclamation, the TS7700 attempts to fill the targeted volume and mark it 100% active. Although the granularity of the percentage of full TS7700T tracks is 1/10 of 1%, it rounds down, so even 1 byte of inactive data drops the percentage to 99.9%. 

## Physical volume reclamation details 

Physical volume reclamation  consolidates active data and frees stacked volumes for return-to-scratch use. Reclamation is part of the internal management functions of a TS7700T. The reclamation process is basically a tape-to-tape copy. The physical volume to 

