IBM TotalStorage 3494 Tape Library, Operator'S Manual

Page: 97 / 605

storage pool of 4. The secondary copy of LOG001 is written to a stacked
volume that is in pool 4. Multiple Management Classes can define the
same secondary pool.
The Peer-to-Peer Copy Mode is used in the PtP environment only. For
non-PTP environments this element is ignored. It controls when a logical
volume is copied to the second PtP library. The options are as follows:
v
Immediate Copy Mode: In this mode, when a host Rewind/Unload
command is received, the copy operation begins. The copy operation is
only performed by the VTC that received the Rewind/Unload
command. When the copy operation completes, the VTC indicates that
the Rewind/Unload is complete. Since the copy operation is executed
during the command execution of the Rewind/Unload command, the
job times for writing a logical volume is longer when compared to the
same job on a non-PtP VTS.
v
Deferred Copy Mode: In this mode, when a host Rewind/Unload
command is received for a logical volume, a copy operation is queued to
every VTC in the configuration. Once the operation is on at least one
VTC copy queue, the VTC indicates that the Rewind/Unload is
complete. The copy is then executed in the background as VTS activity
permits by the first VTC that also has available resources for the copy.
v VTC Defined: Immediate or deferred as defined at the VTC. In a
Geographically Dispersed Parallel Sysplex
™
(GDPS
®
) environment the
VTC Defined mode should be selected. This will prevent the
Management Class defined copy mode from overriding the host or VTC
defined copy mode. Multiple Management Classes can define the same
Peer-to-Peer Copy Mode.
v No Copy: Logical volumes are not copied to the second PtP VTS when
this option is selected.
The PtP I/O VTS specification has three settings.
v
VTC Defined: Selecting this option directs the VTC to select which VTS
acts as the I/O VTS.
v Dist. Library 0: Selecting this option sets Distribution Library 0 (VTS 0)
as the I/O VTS.
v
Dist. Library 1: Selecting this option sets Distribution Library 1 (VTS 1)
as the I/O VTS.
Note: The No Copy option for Peer-to-Peer Copy Mode and the PtP I/O
VTS setting together comprise the PtP Selective Dual Copy feature.
This feature helps minimize wasted bandwidth and storage by
preventing useless information (such as a copy of production data
used for testing updated applications or data generated during a
disaster recovery test) from being copied to the non-I/O VTS.
VE Clusters
Used to enter or view the cluster copy data consistency point values for
each cluster of the IBM Virtualization Engine TS7700 Series. Clicking on
the
Open Panel
button brings up the Cluster Copy Data Consistency Point
panel (Figure 160 on page 259) that is used to change or view the
consistency point values on a per-virtualization engine basis. This button is
only enabled if there is at least one virtualization engine attached to this
Library Manager that has two or more clusters. See “Manage Management
Classes” on page 257.
Chapter 3. Operational Characteristics
71