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Data transfer time
The length of time taken for a block or sector of data to be read from or
written to an I/O device, such as a disk or tape.
Definitive Software
Library (DSL)
The library in which the definitive authorized versions of all software CIs are
stored and protected. It is a physical library or storage repository where
master copies of software versions are placed. This one logical storage area
may, in reality, consist of one or more physical software libraries or
filestores. They should be separate from development and test filestore areas.
The DSL may also include a physical store to hold master copies of bought-in
software, e.g., fireproof safe. Only authorized software should be accepted into
the DSL, strictly controlled by Change and Release Management.
Delta Release
A Delta, or partial, Release is one that includes only those CIs within the
Release unit that have actually changed or are new since the last full or Delta
Release. For example, if the Release unit is the program, a Delta Release
contains only those modules that have changed, or are new, since the last Full
Release of the program or the last Delta Release of the modules.
depreciation
The loss in value of an asset due to its use and/or the passage of time. The
annual depreciation charge in accounts represents the amount of capital assets
used up in the accounting period.
differential charging
Charging business customers different rates for the same work, typically to
dampen demand or to generate revenue for spare capacity. This can also be used
to encourage off-peak or nighttime running.
direct cost
A cost that is incurred for, and can be traced in full to a product, service,
cost center or department. This is an allocated cost. Direct costs are direct
materials, direct wages and direct expenses.
disaster recovery
planning
A series of processes that focus only upon the recovery processes, principally
in response to physical disasters, that are contained within BCM.
discounted cashflow
An evaluation of the future net cashflows generated by a capital project by
discounting them to their present-day value. The two methods most commonly used
are: yield method, for which the
calculation determines the internal rate of return (IRR) in the form of a
percentage: net present value (NPV) method,
in which the discount rate is chosen and the answer is a sum of money
disk cache controller
Memory that is used to store blocks of data that have been read from the disk
devices connected to them. If a subsequent I/O requires a record that is still
resident in the cache memory, it will be picked up from there, thus saving
another physical I/O.
downtime
Total period that a service or component is not operational, within agreed
service times.
duplex (full and half)
Full duplex line/channel allows simultaneous transmission in both directions.
Half duplex line/channel is capable of transmitting in both directions, but only
in one direction at a time.
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