Failure Mode Recovery . The system should be designed so that it is capable of
completely recovering from plant power loss without manual intervention.
System software necessary for computer reboot and operation should be stored
in nonvolatile memory.
Operator Workstations. Operator workstations should have access to the
communications bus so that if one goes out of service, another can assume the
functions of the disabled unit. In general, response time from the completion of a
user inquiry to the completion of resulting display should be 2 seconds. The
availability of easy-to-use graphical interface makes plant operation safer and
more economical. Graphics displays should be user-configurable. Designers
should consider using high-resolution workstations, the ability of the workstations
to be scaled, and color vector graphics that are configured with a computer-aided
design (CAD)-type drawing package.
System Diagnostics. Consideration should be given to providing self-
diagnostics on all circuits (to the smallest replaceable plug-in module or
component) and reporting failures to the operator workstations to indicate the
source of the failure.
Real Time Database. The data base should be hierarchical in structure to
match the controller database. Capability to exchange data with standard third
party applications should be provided.
Data Historian. For trending purposes, the designer should consider use of a
data historian capable of recording both process and system events and off-
loading the records to permanent storage or other computer systems. Data
compression algorithms may be used to minimize long-term storage
4.2.10 Acceptance Tests . Various system hardware and software acceptance tests
should be performed and documented both at the vendor' shop and at the site