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Storage Class
Data Class
Storage Pools
A storage pool contains VTS physical stacked volumes. Within a pool some of the
volumes are scratch and some are private. The private volumes contain logical
volumes with active data. Every VTS stacked volume is assigned to a storage pool.
Each VTS within a 3494 Tape Library has its own set of pools. There is a Common
Scratch Pool (pool 0) which is a reserved pool containing only scratch stacked
volumes. There are also 32 general purpose pools (pools 1-32).
The 3494 Tape Library determines which pool to copy a logical volume to for the
primary copy with the Storage Group Construct. Logical volumes are assigned to
Storage Groups. A Storage Group points to a primary storage pool. When a logical
volume is copied to tape, it is written to a stacked volume that is in the Storage
Pool indicated in the Storage Group assigned to the logical volume.
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3494 Tape Library Operator Guide
Used to define the Tape Volume Cache (TVC) preference for a logical
volume.
The Tape Volume Cache (TVC) preference level has 3 options.
v Use the TVC preference as defined by the IART value specified by the
host to the VTS. Using this option eases the customer's migration from
using the already implemented IART method to using the Storage Class
construct to define the TVC preference levels. The Storage Class can be
setup to use the IART defined value until the time the customer is ready
to use the Storage Class construct.
v Use TVC Preference Level 0. Logical volumes associated with this
preference level have copy priority over volumes with other preferences
and are preferred to be removed from the TVC when space is needed.
Preference level 0 volumes may also be removed from cache as a
background operation during periods of light workload. This option is
useful for logical volumes that probably won't be recalled. Backup data
sets are examples of this. The data will only be recalled in the event of a
disaster.
v Use TVC Preference Level 1. Preference Level 1 will remove a logical
volume from TVC if space needs to be freed in the TVC. This option is
useful for data that has a high probability of being recalled.
The data class is used to select logical volume size in 3494 B10 and B20
VTSs. The size defined by the data class can be:
v Insert media type (sets the logical volume size to that of the media type
that was selected when the logical volumes were inserted; either 400 MB
or 800 MB)
v 1000 MB (1 GB)
v 2000 MB (2 GB)
v 4000 MB (4 GB; only available if the 3494 B10 or B20 VTS has 1.7TB
cache and 3592 J1A Tape Drives or 3592 E05 Tape Drives emulating J1A
attached)
See "Manage Data Classes" on page 264 for information on setting virtual
volume capacity.
Note: Logical volume size might be limited to 2000 MB based on the size
of the tape volume cache within the VTS.
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