EMC Symmetrix DMX-3 Product Guide
317
Glossary
P
page Several commands use regular parameter structures that are referred
to as pages. These pages are identified with a value known as a page
code.
Partitioned Dataset
(PDS) Assist
An IBM feature for 3990 Model 6 and 3990 Model 3 with Extended
Platform units. PDS Assist improves performance on large,
heavily-used partitioned datasets by modifying the directory search
process.
PBX (Private Branch
Exchange)
Short for private branch exchange, a private telephone network used
within an enterprise. Users of the PBX share a certain number of
outside lines for making telephone calls external to the PBX.
physical partition (PP) A physical partition is the smallest unit of disk space that can be
allocated in a volume group in an AIX environment. Any disk space
allocated is an integral number of physical partitions. By default, a PP
is 4 MB in size.
physical ID Physical identification number of the Symmetrix director for EREP
usage. This value automatically increments by one for each director
installed in the Symmetrix system. This number must be unique in
the mainframe system. It should be an even number. This number is
referred to as the SCU_ID.
primary track The original track on which data is stored. See also alternate track.
promotion The process of moving data from a track on the disk drive to a
memory slot.
R
RAID 5 RAID 5 data protection implements data striping and rotating parity
across all hypervolumes of a RAID 5 device. RAID 5 (3+1)
configurations consists of four Symmetrix devices with parity and
data striped across each device. RAID 5 (7+1) configurations consists
of eight Symmetrix devices with data and parity striped across each
device.
read hit The name of the action taken when data requested by the read
operation is in global memory.
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