IBM TotalStorage 3494 Tape Library, Operator'S Manual

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The 3494 Tape Library determines which pool, if any, to copy a logical volume to
for the secondary copy by using the Management Class construct. Logical volumes
are assigned to a Management Class. A Management Class can point to a
secondary storage pool. If the Management Class specifies a secondary storage
pool of zero, a secondary copy of the logical volume isn’t made. If the secondary
pool specified by the Management Class is one of the general purpose pools (1-32)
a secondary copy of the logical volume is made to a stacked volume in the
specified pool.
If FC 4001-4004, Advanced Policy Management, is not installed, the Library
Manager and the VTS will use pools 0 and 1 by default. Pool 0 will be used for
scratch stacked volumes and pool 1 will be used for stacked volumes containing
active data.
Common Scratch Pool (Pool 00): The Common Scratch Pool (CSP) can be used by
the 32 general purpose pools as a reserve from which scratch stacked volumes can
be borrowed or taken from when they run out of scratch stacked volumes
themselves. Pool properties determine whether a General Use pool can borrow
volumes from the CSP. The CSP is pool 0 and contains only scratch stacked
volumes. Stacked volumes in the CSP do not contain any active data.
32 General Use Pools (Pools 01 — 32): There are 32 General Use Pools per VTS.
They are numbered 1 - 32. General use pools can contain both scratch stacked
volumes and private stacked volumes. A general use pool can be set up to borrow
or take scratch stacked volumes from the CSP if they run out of scratch stacked
volumes. For example, pool 2 is setup to borrow volumes from the CSP. A logical
volume needs to be copied to a stacked volume in pool 2 but there are no more
scratch stacked volumes in pool 2. A scratch stacked volume is transferred
(borrowed) from the CSP by pool 2. The logical volume can now be copied to the
newly borrowed stacked volume. The borrowed stacked volume is returned to the
CSP when it is reclaimed since pool 2 is set up to return borrowed stacked
volumes.
Bulk Volume Information Retrieval
This function allows an MVS host to request information about the logical volumes
managed by a VTS, including PtP VTS configurations. The MVS host can retrieve
information about the logical volumes currently in the VTS cache, the logical
volume-to-physical volume mapping on the VTS backstore tapes, and data levels
and validity flags from the VTS token database.
Maintaining Data Fragments from Copied Volumes
When the cache space occupied by a closed virtual tape volume is needed for
other active virtual volumes, the data it represents is not removed completely. A
fragment of the data is kept on disk storage. The data fragment includes
information about the copied virtual volume so that it can be recalled and it also
includes the first several records from the last use of the volume. Normally, the
first few records on a tape contain a tape volume label, and enough data records
are maintained to contain an IBM standard tape label plus any unique user label
records.
Fast Response for Nonspecific Mount Requests
When a nonspecific mount is requested, the user application will write data from
the beginning of tape, overwriting any existing data on the tape. The host can
request a nonspecific mount in a 3494 Tape Library by specifying a category
instead of a specific volser in the mount request. The Library Manager then selects
Chapter 3. Operational Characteristics
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