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EMC Symmetrix DMX-3 Product Guide
Glossary
B
backplane Card that accommodates the channel directors, disk directors, global
memory directors, channel adapters, and the XCM.
bit The smallest unit of computer memory. A bit can hold a value of zero
or one.
business continuance
volumes (BCVs)
A standard Symmetrix device with special attributes that allow it to
independently support applications and processes, such as backup
operations, restore operations, Decision Support operations, and
application testing. BCV devices are available through the EMC
TimeFinder software.
byte Any 8-bit unit of data storage.
C
cache See Global Memory.
cache slot Unit of cache equivalent to one track.
channel director The component in the Symmetrix subsystem that interfaces between
the host channels and data storage. It transfers data between the
channel and global memory.
CCOPY Concurrent Copy Facility used on IBM DASD.
command descriptor
block (CDB)
The structure used to communicate commands from an initiator to a
target. This structure may be 6 bytes, 10 bytes, or 12 bytes in size.
Compatible Parallel
Access Volumes
(COM-PAV)
Compatible Parallel Access Volumes is an IBM feature, supported by
the Symmetrix unit, that improves response time, resulting in greater
resource availability to the host.
controller ID Controller identification number of the director that the disks are
channeled to for EREP usage. There is only one controller ID for the
Symmetrix unit.
Count-Key-Data
(CKD)
A data recording format employing self-defining record formats in
which each record is represented by a count area that identifies the
record and specifies its format, an optional key area that may be used
to identify the data area contents, and a data area that contains the
user data for the record. CKD can also refer to a set of channel
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