Digital Equipment DEC 3000 Series Service Information page 408

disk drive
A device that holds a disk. The drive contains mechanical
components that spin the disk and move the read and write heads
that store and read the information on the surface of the disks.
diskette
A disk contained in a square jacket. Diskettes can be inserted
and removed from diskette drives.
diskette drive
A disk drive that reads from or writes to a removable diskette,
such as an RX26 diskette.
diskless system
A system that has no storage capacity of its own.
distributed processing
A processing configuration in which each processor has its
own autonomous operating environment. In a distributed
processing environment, the processors are not tightly coupled
and globally controlled as they are with multiprocessing. Instead,
an application is distributed over more than one system. The
application must have the ability to coordinate its activity over a
dispersed operating environment.
DMA
See direct memory access.
DRAM
See dynamic random-access memory.
dynamic random-access memory (DRAM)
Read/write memory that must be refreshed (read from or written
to) periodically to maintain the storage of information.
ECC error
Describes a memory error. There are two kinds of ECC errors.
ECC correctable errors are errors that are successfully corrected
by the error detection and correction process. ECC uncorrectable
errors are not successfully corrected by this process.
environment variable
A global data structure that can be accessed only from console
mode. The setting of these data structures determines how a
system powers up, boots operating system software, and operates.
error correction code (ECC)
Code that carries out automatic error correction by performing an
exclusive OR operation on the transferred data and applying a
correction mask.
Glossary–8