DEC 4000 AXP Service Manual page 232

volume shadowing
The process of maintaining multiple copies of the same data on two or more disk
volumes. When data is recorded on more than one disk volume, you have access
to critical data even when one volume is unavailable. Also called disk mirroring.
Vterm module
The module located behind the OCP that provides the termination voltages for
storage bus E. The Vterm module also contains the logic for reporting SCSI
continuity card errors.
warm bootstrap
A subset of the cold bootstrap operations: during a warm bootstrap, the console
does not load PALcode, size memory, or initialize environment variables.
warm swap
The shutdown and removal and replacement of a failing DSSI disk from an active
bus.
word
Two contiguous bytes (16 bits) starting on an arbitrary byte boundary. The bits
are numbered from right to left, 0 through 15.
write back
A cache management technique in which data from a write operation to cache is
written into main memory only when the data in cache must be overwritten. This
results in temporary inconsistencies between cache and main memory. Contrast
with write through.
write-enabled
A device is write-enabled when data can be written to it. Contrast with
write-protected.
write-protected
A device is write-protected when transfers are prevented from writing information
to it. Contrast with write-enabled.
write through
A cache management technique in which data from a write operation is copied to
both cache and main memory. Cache and main memory data is always consistent.
Contrast with write back.
Glossary–22