HP 3000 Manuals HP 3000 Manuals
Appendix D Glossary
Advanced Terminal An intelligent hardware interface between terminals and the
Processor (ATP) Central Processing Unit (CPU) interrupts. It supports
full-duplex asynchronous modems and direct memory access of
user data.
American Standard Code The standard method of representing character data (seven data
for Information bits plus one that is sometimes used for parity). This method
Interchange (ASCII, was (ANSI) to achieve compatibility between data devices when
USASCII) they are interchanging information.
ASCII Refer to American Standard Code for Information Interchange.
Asynchronous Data A terminal controller serving as the hardware interface
Communications between the Central Processing Unit (CPU) and the terminals
Controller (ADCC) connected to the system (either directly or via modem). Each
main ADCC supports four terminals and an extender ADCC. The
extender adds an additional four ports for a combined maximum
of eight terminals supported per ADCC.
Backup The process of duplicating computer data on an offline media,
such as magnetic tape or serial disc. This preserves data
should a system crash occur. The term backup is also used to
describe data, (backup files), or media (backup tape).
Central Processing Unit The part of a system that interprets and executes instructions
(CPU) and contains all or part of internal storage. The central
processor contains an Execution Unit and a Control Unit.
Communications Line A communications link between two systems, for example, a DS
line.
Communication Process A Silhouette process that exists as the major component on the
(CP) primary system and a minor component on the secondary system.
On the primary system it reads the data from the logfile and
transmit it to the Secondary Communication Process (SP) on the
secondary system.
Command Interpreter(CI) A program that reads lines of text from standard input
(entered at the keyboard or redirected from a file), and
interprets them as requests to execute other programs. The
Command Interpreter for MPE is called the CI.
Configuration File An ASCII file containing the various parameters describing the
environment for a Silhouette system.
Console Refer to System Console.
Control Unit A part of the CPU that regulates the Execution Unit and
oversees the instruction cycle.
Database An integrated collection of logically related data and the
structural information about the data.
Database Management A software package designed to protect the consistency and
System (DBMS) security of data in computer-stored files (databases). It
allows a user to define a database structure and manipulate
the contents by storing retrieving, deleting, modifying, and
sorting data.
Data Item The smallest accessible data element in a database. A data
item corresponds to a column in relational database
terminology.
Distributed System Line The communications line between two computers, controlled by
(DS Line) the Distributed System Network.
Distributed System A system of hardware and software data communications products
Network (DSN) spanning multiple Hewlett-Packard product lines.
Duplication The process of duplicating and keeping an identical database
up-to-date on one or more remote (secondary) systems.
EDIT/3000 An HP 3000 text editor, supplied with MPE V/E. It is used to
create and manipulate ASCII files.
Editor A common operating system utility program used in the
preparation and modification of text and program files.
EDIT/3000 is one of the text editors used with the HP 3000.
Execution Unit(EU) The part of the CPU containing the Arithmetic (ALU) and the
registers. Data is held in registers and manipulated in the
ALU.
Heartbeat A self-monitoring feature of Silhouette. A missed heartbeat
will be reported to the Operator, by either the primary or
secondary system, or both if the DS line is broken.
High Water Mark A specified limit as to the number of records allowed to
accumulate in the buffer on the primary system after which
they will be copied to tape for use in restoring the secondary
system.
Intelligent Network A communication input/output board used with Hewlett-Packard
Processor (INP) data communications products.
LG Capability Refer to User Logging Capability.
Load Balancing After application programs are copied onto a secondary system,
they can access the secondary database in read mode to perform
the processing load on the primary system resulting in
improved system performance and response time.
Logfile A file that maintains a record of events. Each event is
recorded in a separate log record, and is correlated with the
job or session causing the event.
Manager Program (MP) A Silhouette process used to communicate with the
Communication Process. It is used to begin Silhouette, to
display the current status of Silhouette, or initiate a backup
on the secondary system. All Silhouette commands are issued
at the MP chevron prompt (>).
Message Files Message files are used by Silhouette processes to communicate
with each other. This communications requires two message
files; one for sending data and one for receiving data.
Multiple Transaction A multiple transaction involves several modifications to a
database. Adding a sales record and updating the total sales
counter is a multiple transaction since two modifications are
made to the database.
Primary/Secondary A relationship between two processes in which one initiates
the execution of the other, and controls all subsequent
communications between them.
Primary System An HP 3000 used as the device where the original database is
created, modified, and then duplicated to the secondary
system. There can be multiple primary systems for each
secondary system. Users on the primary may access the
original database in READ and WRITE mode.
Record A collection of fields or related data treated as a unit,
residing in a file. A contiguous group of bytes whose
structure is known by the file system.
Recovery Process (RP) A Silhouette process that exists only on the secondary system.
It accepts data from the Secondary Communication Process (SP)
and updates the database and logfile with the data.
SAVE File The SAVE file exists only on the secondary system and is used
by Silhouette to store information about records transmitted
to the duplicate logfile and also those already processed
against the duplicate database.
Secondary Communication A Silhouette process that exists on the secondary system where
Process (SP) it creates the Recovery Process (RP) if one does not already
exist, accepts data from the Communication Process (CP) on the
primary system, and sends the data to the RP via message
files.
Secondary System An HP 3000 used to maintain a duplicate copy of a database.
The duplicate copy of the database is kept up-to-date. There
can be multiple secondary systems for each primary system.
Users on the secondary system(s) may access the duplicate
database in READ mode only.
Silhouette An add-on product for the MPE operating system on the HP 3000.
It allows dynamic duplication of databases from a primary
system to a secondary system(s). This provides high
availability of the system, backup of databases without
interrupting primary system operation and better system
performance by load balancing.
Single Transaction A database transaction involving one modification. Deleting a
record from a dataset is an example of a single transaction
since only one modification is made to the database.
Super Transactions A super transaction is a logically connected series of
transactions spanning multiple databases or multiple database
paths.
SWITCH The process of making the secondary system the primary system
in the event of a failure on the original primary system.
System Console A workstation given a unique status by the operating system.
It is used by the Operator to execute specific commands for
the purpose of managing sessions, job, and system resources.
It is associated with all error and certain status messages.
System Manager The person who manages the computer installation, responsible
for creating accounts and assigning capabilities and resource
use limits to each.
System Supervisor A capability assigned by the System Manager to the System
Capability (OP Supervisor's user name and account. The System Supervisor is
Capability) responsible for performing backups, altering the system
configuration, and in general, managing the overall operation
of the HP 3000.
Tape Process(TP) A Silhouette process created by the Communication Process (CP)
on the primary system only. It is activated when the backlog
of records in the logfile exceeds the predefined high water
mark.
Terminal A hardware device connected to a computer, used for entering
and receiving data. A terminal consists of a keyboard and a
display screen.
TurboIMAGE A database management system consisting of a set of programs
and procedures used to define, create, access, and maintain a
database.
User Logging Capability User Logging Capability (LG) capability allows the user to
(LG) create a journal of additions and modifications to databases
and subsystem files. User Logging permits this journal to be
sent to tape or disc. If the database is lost, the logging
tape or disc file can be used to recover the lost
transactions.