Setting Up Data Management Definitions For Copy Export - IBM TS7700 Series User Manual

August 15, 2017

Setting up Data Management Definitions for Copy Export

With DFSMS, you control where data is stored and how it is managed through a set of names associated
with a logical volume during allocation. The names are called storage constructs, and storage construct
names have policies associated with them that define where and how data is stored and managed. One of
the constructs, Storage Group, is used to manage where the primary copy of a logical volume's data is
stored. For the TS7700, a group of physical data storage cartridges, referred to as a physical volume pool,
can be associated with a storage group construct name. Logical volumes that are assigned the storage group
name are copied from the tape volume cache to the physical volume pool associated with that name.
Another construct, Management Class, is used to control where additional copies of the logical volume are
to be made. One of the options of management class is to specify that a second copy of a logical volume is
to be made. Like storage group, a physical volume pool is associated with a management class name to
hold the secondary copy. Logical volumes that are assigned the management class name are copied to the
physical volume pool associated with that name. Using management class to specify a secondary pool
allows for two copies of a logical volume's data to be stored in the TS7700, each on a separate physical
volume, to provide for recovery if the primary physical volume is damaged or misplaced. This ability to
make a second physical copy of a logical volume's data is core to the copy export function.
A TS7700 supports up to 32 different physical volume pools. Normally, a physical volume pool can be
used as a storage location for either a primary or secondary copy of a logical volume's data, but no
restriction is made to prevent storage group and management class name definitions to specify the same
pool number. With copy export, this changes. A physical volume pool that is to be used for copy export
cannot contain the primary copy of any logical volume's data, because then a subsequent copy export would
remove that primary copy. A pool's properties definition must explicitly specify whether or not it will be
used for copy export. If a pool's properties indicate that it is to be used for copy export, the pool cannot
later be associated with a storage group name definition. If a pool is already associated with a storage group
name, the pool's properties cannot be modified to indicate that it is to be used for copy export.
Note: In setting up for copy export, you are not restricted to defining a single physical volume pool for copy
export. You may want to define more than one management class with an associated different physical
volume pool for data that is to be copy exported to different sites or to keep like application data together.
For copy export, you will be defining at least one additional physical volume pool. As part of that
definition, you will need to decide how physical volumes become part of a pool and how they will be
reclaimed.
Physical volumes become part of a physical volume pool either by 1) being explicitly assigned to the pool as
the volumes are inserted into the library, or 2) by being borrowed from the common scratch pool when
needed or 3) moved to the pool using the move physical volumes function of the TS7700 or the stacked
volumes function on the library manager for pre 8.5.x.x systems. Prior to inserting physical volumes, if
volumes are to be explicitly assigned to a pool during insert, set up a volume serial number range for a
specific pool using the Physical Volume Ranges on the TS7700 or the Volser Range window on the library
for pre 8.5.x.x systems and 3494 attached libraries. A pool can 'borrow' physical volumes from the
common scratch pool when needed and optionally 'return' them to the common scratch pool when they
have been reclaimed. Borrow and return rules are also specified as part of the definition for a physical
volume pool. With the move physical volume function, one or more scratch physical volumes can be
moved from one pool to another. A physical volume that has valid logical volumes on it can also be moved,
however, the logical volumes are first copied to another physical volume in the originating pool.
There are six primary steps in setting up the data management definitions and controls for copy export:
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