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are less than 10 scratch stacked volumes, the Inhibit Reclaim Schedule shown on
the Set VTS Management Policies pop-up window, Figure 99 on page 169, will not
be in effect and the VTS will proceed to reclaim space on stacked volumes until at
least 15 scratch stacked volumes are available. This activity may affect the
performance of the host jobs running on the VTS.
Integration with the 3494 Library
A Virtual Tape Server subsystem must be associated with an IBM library because
the physical assets used by the subsystem are managed by the library manager in
the library. The physical assets include the 3590 tape drives and the 3590
cartridges used for stacking logical volumes. The library manager provides several
other key functions involving a Virtual Tape Server subsystem. These functions
include:
v Logical library partitioning
v Operator interface
v Logical volume inventory
Logical Library Partitioning
To support the product requirement that a Virtual Tape Server subsystem can
coexist with current 3490 and native 3590 subsystems in the same library, the
library manager partitions the physical library into logical libraries. This must be
done because a Virtual Tape Server subsystem presents the image of 3490-type
tape drives, and yet cannot read or write a real 3490 cartridge. By placing a Virtual
Tape Server subsystem in its own logical library, host software will not be able to
attempt to allocate a Virtual Tape Server drive for a real 3490 mount and vice versa.
A logical library can contain either of the following:
v A single Virtual Tape Server subsystem
v Current 3490 or native 3590 subsystems
Each logical library will have its own unique library sequence number and will look
like a separate physical library to the hosts attached to the subsystems in that
partition.
Note: Currently, up to two Virtual Tape Servers (only one of which may be a Model
B16) are allowed in a physical library.
SCSI Host Attachment
The SCSI Host Attachment feature provides attachment to RS/6000 systems. The
sharing of a VTS among S/390 and RS/6000 systems requires assignment of virtual
drive usage in a manner similar to stand-alone tape drives. Because only one host
system at a time can use a drive, the drive has to be dedicated to that host during
processing.
For a detailed discussion on tape library sharing between S/390 and SCSI hosts,
including considerations about drive sharing, volume sharing and related software
implementation steps, refer to
Guide to Sharing and Partitioning IBM Tape Library
Dataservers
, SG24-4409. The SCSI target addresses are discussed in
IBM 3494
Tape Library Introduction and Planning Guide
, GA32-0279.
44 Magstar 3494 Tape Library Operator Guide
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