Glossary

This glossary defines the special terms used in the Reality documentation. For the most part, the terms defined are specific to Reality. However, a few general data processing terms that are used in this documentation are also defined. All terms are presented in alphabetical order.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

ACC File

The account history file records statistics for user logon sessions. These include date and time of logon, duration of logon session, CPU time used, the PLId of the logged on process, and the account logged-on to. ACC is held in the SYSFILES account.

Account

A set of files and commands and other characteristics, defined by the account's Master Dictionary and the definition item in SYSTEM file for the account, that define the facilities available to users logged-on to that account (qualified by the user's profile). For example, on a particular database (as defined by a unique SYSTEM dictionary), you might have an 'accounts payable' account, a 'word processing' account, and a 'program development' account. Accounts are comparable to the term 'directory' as used in UNIX and Windows systems.

Account-based Security

Account-based security consists of update and retrieval lock codes on files, and passwords to logon to accounts. See also Location-Based Security and User-Based Security.

Account Definition Item

An account on a Reality database is defined by an Account Definition Item residing in the SYSTEM dictionary. The item is a D-pointer to the account's Master Dictionary. It defines the following attributes of an account:

Account name.
Modulo and separation for the Master Dictionary.
Retrieval lock code(s).
Update lock code(s).
Password.
System privileges.
ACC file update status.

Account Synonym Definition Item

A Q-pointer that defines an alternative name for an account and can define different facilities for users logged-on via that name, as given by attributes similar to those in the Account Definition Item.

ACI

Asynchronous Character Interface (networking) – an ACI circuit is a character mode circuit.

Advisory Locks

Locks that are not enforced by the file system. On Reality, item locks are "advisory".

AFI

Authority and Format Identifier (networking) – part of an NSAP address.

AFS File

A data section or index that has been configured for automatic file sizing.

ALL

An acronym for Application Language Liberator. Northgate's proprietary fourth generation application program development tool.

AMC

An abbreviation for Attribute Mark Count. The AMC is a number contained in attribute 2 of a data definition item that points to the data attribute (line) defined by the dictionary item.

ANSI

An acronym for American National Standards Institute. The American representative to the International Standards Organisation.

API

Application Programming Interface - a set of functions that you can use in your programs to work with a component.

Array

A set of data identified by a single name. Specifically, a variable used in DataBasic programs that has multiple values.

ASCII

An acronym for American Standard Code for Information Interchange.

Attribute

A first-order subset of an item. Attributes are groupings of item data, separated by attribute marks, that share a particular property. Within the EDITOR, an attribute is one line.

Attribute Definition Item

See Data Definition Item.

Attribute Mark

A character used to separate attributes. Reality uses X'FE' (decimal character 254; CTRL+^, from the keyboard) as the attribute mark. It is converted to a ^ character X'5E' by some processors for display purposes.

Automatic File Sizing

A mechanism by which files expand automatically as they are updated. They can also be forced to expand or contract if required.

B

Baud Rate: The number of signalling elements per second. A measure of the signalling rate of a data channel. The data transfer rate measured in bits per second is usually (thought not invariably) a simple multiple of this.
Bit: A contraction of Binary digit. Bits take on the values 0 or 1 only. The bit is the basis for all modern digital computation.
Bits Per Second (bps): The number of bits transmitted per second. Depending on the coding scheme, many bits can be transmitted per baud. This means that you can have a much higher bit rate than baud rate, but never the reverse. Compare with Baud Rate.
BLOCK-CONVERT File: The file that contains the definitions of the characters used in the BLOCK-PRINT and BLOCK-TERM commands. BLOCK-CONVERT is held in the SYSFILES account.
Boolean: A data type that can take only the values TRUE and FALSE. TRUE is normally defined as any non-zero integer, and FALSE as 0 or a null string. Any other values generate a run time error.
Bus: A parallel data pathway between central elements of a computer.
Byte: A unit of storage comprising 8 bits and capable of holding a single string character. In Reality, each character is one byte.
Byte Order: The order in which the bytes that make up values larger than 255 are arranged in a computer's memory. This depends on the CPU's architecture. For example, Solaris and AIX systems have normal byte order (high order bytes precede low order bytes), while Intel systems running Windows and Linux have reversed byte order (high order bytes precede low order bytes). Physical backups of Reality cannot be restored on hosts with different byte ordering.

C

CCI

Consistent Circuit Identifier. An integer corresponding to one or more Physical Location Identifiers (PLIds). A CCI is assigned via the NETWORK file. It can be found for the current process using the DataBasic SYSTEM(48) function.

CCITT

Consultative Committee for International Telegraph and Telephone, an international standards organisation for the voice and data communications industry.

Character Entity

An alternative way to specify a text character in HTML. Character entities should be used when you need to display characters that have special meaning to the browser, such as the less-than and greater-than symbols, and the ampersand character. Refer to your HTML documentation for more details.

Character Mode

A terminal circuit where the terminal input and output is presented directly onto the transport mechanism, with no additional protocol (networking).

Class

Part of a DDA CONNECT message (networking). The class identifies the type of connection – that is, terminal or client/server.

Client

A process that requests a service from another, server process.

Client-id

Part of a DDA CONNECT message (networking) – identifies the calling system and user.

Column

A location within an SQL database table that stores a particular type of data. In a data sheet, a column is a vertical stack showing the value of a field in every record. Individual columns have their own specifications as to data type and maximum length. These are called column (or field) properties.
In HTML, a vertical arrangement of text, table cells or frames.

Compile

To translate an entire source language program to machine-executable format before running the program. Compare with Interpret.

Conversion

Processing performed on data by an English command. Conversions are specified in attributes 7 and 8 of a Data Definition Item. Those in attribute 8 (V/CORR) are performed before sort/selects, those in attribute 7 (V/CONV) after sort/selects (immediately before output).

Cookie

A small amount of named data stored by a web browser and associated with a particular web page or site. Cookies serve to give the web browser a memory, so that it can recall user preferences or other state variables when the user leaves a page and subsequently returns, or can pass data between pages.

Correlative

See V/CORR.

CPU

Central Processing Unit.

CSS

Cascading Style Sheet - a mechanism by which the presentation of an HTML page can be separated from the content. A style sheet can be used to determine the appearance of one or more HTML pages.

CSV

Comma-separated values. A host file format where each line of a text file contains a data record, with the fields in each record separated by commas. Fields containing commas are enclosed in quotation marks. The first line of the file is normally a header containing the names of the data fields.

Other delimiters are sometimes used (for example, tabs).

D

D-pointer

An item in a dictionary with D/CODE D that points directly at a lower level data structure. The lower level structure can be another dictionary or it can be a data section.

D/CODE

Attribute 1 of any type of Dictionary Definition Item. Valid D/CODE values include A, D, DL, DX, DY, M, Q, R, S, and X; for details, see File and Item Structures.

Daemon

A server process on a UNIX system.

DAT

Digital Audio Tape, a type of magnetic tape that uses a scheme called helical scan to record data. DAT cartridges can hold from 2 to 24Gbytes of data, at data transfer rates of about 2Mbytes per second.

Data Definition Item

A dictionary item that defines the properties of an attribute such as a heading for listing the data, conversion codes, and so on.

Data Dictionary

See File Dictionary.

Data Level

See Data Section.

Data Section

A file at the lowest level of the database used to store raw data.

Data Type

The attribute of a variable or field that determines what kind of data it can hold. This is specified in field 1 of the column definition (SQL).

Database

A collection of data stored in an organised manner, independent of physical layout, that enables the data to be accessed easily by users. For Reality, this describes each collection of data in the host file system that is organised into accounts and files. A number of these Reality databases can exist on one host. Each is defined by a unique SYSTEM dictionary.

Database Management System

A computer software system for managing stored information and providing protocols and a language interface to define, access, and change that information.

Database Owner

The host user who created the database.

DataBasic

A high level, compiled programming language available with the Reality environment. DataBasic is a greatly extended version of Dartmouth BASIC that has been highly optimised to deal with Reality data structures.

DBMS

Database Management System.

DDA

Distributed Data Access – DDA is a Northgate communications architecture which allows physically remote systems to make connections and transfer data. When DDA is in use, data is sent across a connection in DDA message format (packages of data). For details of the format of DDA messages, see the Reality C API documentation.

Deadly Embrace

A situation in which two processes are competing for items locked by the other. For example, suppose Process A asserts a lock on Item B and then attempts to assert a lock on Item A. Simultaneously, Process B asserts a lock on Item A and then attempts to assert a lock on Item B. Process A and Process B each are asserting an item lock on an item the other process also requires. The result is a stalemate in which neither process is able to gain access to all the items it requires.

Default

The action taken by the system or application when no explicit instruction is issued by the user.

Delimiter

A character used to set off a string of data. Reality uses characters known as system delimiters, which include attribute, value, subvalue, segment, and start buffer marks to delimit system data.

Denationalisation

The capability to display error and system messages in a specified language (or multiple specified languages on a port-by-port basis). Denationalisation also allows you to specify your own decimal, money sign, and thousands separator symbols, convert characters for output and define alternative sort sequences.

DES:CBC

Data Encryption Standard : Cipher Block Chaining – DES is a method of data encryption in blocks of 64 bits using a two way key of 64 bits. CBC is one of three algorithms that can be used by DES, whereby the encryption of each block differs depending upon the contents of preceding blocks.

Destination entry

An entry in the ROUTE-FILE that describes how to connect to a remote system (networking).

Device driver

Software which controls a device; for example, LAN controller software (networking).

DHTML

Dynamic HyperText Markup Language - a mechanism for adding active content to web pages.

DICT

A mnemonic that specifies a dictionary file.

Dictionary

A file that defines lower level files. The file defined by the dictionary can either be a data file or another dictionary.

Dirty Read

A situation in which Transaction T1 updates an item but does not commit before Transaction T2 reads the same updated item, and then Transaction T1 aborts, necessitating the undoing of all its updates. Transaction T2 is said to have read a non-existent, or "dirty," item. The term applies only to Transaction Handling.

DLL

Dynamic Link Library. A mechanism that allows Windows programs to share code, thus reducing the memory requirements when running multiple applications. A DLL is loaded into memory only when required, and can be removed again to make room for other code.

DLT

Digital Linear Tape. A type of magnetic tape storage device that uses ½-inch wide tape in cartridges, with capacities ranging from 20 to over 40Gbytes. DLT drives are faster than most other types of tape drives, with transfer rates of 2.5Mbytes per second.

The latest Super DLT (SDLT) devices have capacities between 300 and 600GBytes and transfer rates of 72Mbyes per second over high-speed media.

DNS

Domain Name System. Resolves network names to IP addresses.

Download

Copying software from a device remote to you into a device local to you.

DSP

Domain Specific Part – part of an NSAP address (networking).

Dynamic Array

A multi-element string variable in which data is divided into elements by attribute marks, value marks and subvalue marks, matching the structure of a Reality file item. The entire array is referenced and stored as a single variable. For more information, refer to the DataBasic Reference.

E

Echoplex: A procedure commonly used by asynchronous terminal handlers in which each character sent from a user's terminal to the computer is sent back (echoed) to the sending terminal's video screen.
EIA: An acronym for Electronic Industries Association, an American standards organisation for the electronics industry. RS-232-C is an EIA standard.
Encryption: The encoding of data so that it may be read only by authorised persons. Data is transformed in a way that can be reversed only by someone who possesses an extra piece of information called the key.
English: The Reality database query language.
English Macro: An English facility you can use to reduce keyboard input for frequently used database queries. See English Macros for details.
ERRMSG File: The file that contains many of the Reality error messages. The ERRMSG file is held in the SYSFILES account. Each Master Dictionary contains a pointer to ERRMSG.
Ethernet: A local area network protocol (IEEE Standard 802.3).
Ethernet address: Each system on a LAN has an address which can be used by other systems to access it. An Ethernet address consists of 12 hexadecimal characters and is a hardware address, unique to a particular LAN controller.
Event log: A host file which is used by the session manager to record information about remote connections (networking).
Execution Locks: Execution locks prevent a user-defined entity (process, file, group, direct print file, and so on) from being updated or accessed by more than one process at the same time. Execution locks are not defined by the system, but by a programming organisation responsible for creating a body of application programs. At the level of the item, item and execution locks provide the same function. Because execution locks provide a more extensive locking capability, they are useful for applications such as printing invoices where many data elements must be frozen for the duration of an operation. Execution lock numbers are under user control from Proc and DataBasic using the PLn command and LOCK and UNLOCK statements, respectively.
External routine: A DataBasic external subroutine or function. A separately compiled and cataloged program module.

F

FailSafe Database

An optional Reality configuration in which two identical databases are maintained on separate systems, interconnected by a Local Area Network, to provide a good level of database resilience if a failure occurs. One database, called the primary, is the live database to which users can log on to. The other database, called the secondary, is maintained as the standby. Updates performed on the primary are automatically copied to the secondary, then, in the event of a failure, the standby secondary can be re-configured quickly as the live database so that users can logon again with only a short break in service.

FEATURES File

The file that defines the features on a database and their release levels. Held in ld in ld in SYSFILES.

Field

A single piece of data in an item, usually known as an attribute or line.

Field Read

A facility used to exchange data with a remote terminal. When the field read facility is enabled, input line editing is handled by the remote terminal.

File

A collection of related Reality items associated with a filename that is unique in an account.

File Allocation

File allocation on a Reality Database means to assign a modulo file. This defines the number of groups in the file.

File Definition Item

Each file on a Reality database is defined by a File Definition Item (D-pointer) that is contained in the SYSTEM Dictionary for accounts, in an account's Master Dictionary for data dictionaries, and in the data dictionaries for data sections. The item-id of the file definition item is the file's name. The item also includes:

Retrieval lock code(s).
Update lock code(s).
V-code sublist.
Output alignment code.
Output column width code.
Reallocation parameters.

File Dictionary

A file that defines the attributes and location of data sections.

File Server

A process that resides on a remote system on a network. It retrieves the requested files and returns them to the host system.

Filestore Database

A database in which each Reality file is represented by a file on the host. Filestore databases can only be used on UNIX hosts. See Database Types for more information.

File Synonym Definition Item

A Q-pointer (giving a synonym name) to a file, typically one that is defined on another account.

Firmware

Programs stored in hardware, or Read Only Memory (ROM). Firmware typically, but not always, refers to microprograms stored in ROM. Assembly language and high level language programs can also be stored in firmware. High level language programs stored in firmware are also called embedded applications.

Formqueue

A queue, created by the user, that is normally associated with a printer.

Fragmentation

A state in which the frames making up a file are scattered across the disk rather than being clustered within the same sector or track. This condition slows system performance because it increases the number of disk reads required to bring a file's data into main memory.

Frame

In a Reality database, a single block of disk space (normally 1 kilobyte in size, but can be configured to be 2, 4 or 8 kilobytes).
In HTML, a mechanism by which a browser window can be divided into sections, each of which contains a different web page.

Full network

OSI full network. This uses NSAPs as LAN addresses instead of physical addresses.

G

GFE: Group Format Error. Corruption that causes the structure of a file to be invalid.
GPF: General Protection Fault.
Group: A group is a file subdivision used by Reality to optimise retrieval of items. The modulo of a file determines the number of groups and is set by the creator of the file. See Hashing.
Group Format Error: See GFE.

H

Hashing: A technique for optimisation of the storing and accessing of data using groups. The group an item is stored in depends on its item-id. Reality uses the numerical value of the item-id and the modulo to determine the location (group) of the item.
Hexadecimal: A system for counting in base 16. The digits are 0-9 and A-F.
Hold File: A spooler file stored on the disk until it is explicitly despooled by a user request.
Host: The computer where your database resides.
HTML: HyperText Markup Language. A document layout and hyperlink specification language, used to format web pages.
HTTP: HyperText Transfer Protocol. The underlying protocol used by the World Wide Web.

I

IDI

Initial Domain Identifier - part of the NSAP address (networking).

IDP

Initial Domain Part - part of the NSAP address (networking).

IEEE

Institute of Electrical and Electronics Engineers – an American professional organisation. Creates and publishes various standards, often jointly with ANSI.

Index

An SQL feature that speeds up searching and sorting in a table based on key values and can enforce uniqueness on the rows in a table. The primary key of a table is automatically indexed. Some fields cannot be indexed because of their data type.

Indexing

A Reality feature which enables the creation and use of indexes for accessing a data section so as to improve access time by Reality processors, such as English, TCL and DataBasic.

Inner join

A Join in which records from two SQL tables are combined and added to a query's results only if the values of the joined fields meet a specified condition. For example, when designing a query, the default join between tables is an inner join that selects records from both tables only if the values of the joined fields are equal.

Interactive File Access

A facility which allows UNIX programs to access Reality files.

Interpret

To translate each statement of a program as it is executed and each time it is executed. This contrasts with compilation, where all program statements are translated once.

I/O

Input/Output. A reference to data moving into a processor from an input device, being processed, and moving out of the processor to an output device. With regard to terminal I/O, the input device is a keyboard and the output device is a monitor.

IPC

Interprocess Communication. Allows communicating programs to exchange data and control messages over the network.

ISO

International Standards Organisation. A multinational body that develops and publishes technical standards.

Item

A Reality data structure comparable to the standard data processing structure called a record when values and subvalues are not used, and comparable to the standard data processing structure called a file when values and subvalues are used.

Item-id

An item identifier. A character string that names an item uniquely (within a file). Equivalent to the standard data processing structure called a key or access key. The item-id is also known as attribute 0 of an item.

Item-ids can be from 1 to 240 bytes long, using ASCII characters in the range X'20' to X'FA'. If you specify an item-id that contains one or more system delimiters (characters X'FB' to X'FF'), Reality will truncate it immediately before the first system delimiter.

Item Deadlock

See Deadly Embrace.

Item Locks

Item locks can be used to prevent an item from being accessed by more than one process at the same time. This maintains the integrity of the database while allowing multiple users access to other items in the same group. Item locks are under user control from DataBasic using the READU, READVU, MATREADU, WRITE, WRITEU, WRITEVU, MATWRITEU, RELEASE, and WRITEV statements and from Proc using the FUREAD and F-BU commands. The EDITOR, some TCL commands, and ALL use item locks by default.

J

JavaScript: A programming language supported by most web browsers. Client-side JavaScript allows executable content to be included with web pages.
JDBC: Java Database Connectivity. A Java standard interface which makes applications independent of the database management systems from which they derive their data.
Join: An association between a field in one SQL table or query and a field of the same data type in another table or query. A join tells the Reality SQL server how data is related.
JRE: Java Run Time Environment. Software that makes it possible to run programs written in Java.
JVM: Java Virtual Machine - Java runtime system.

K

Kbyte: 1024 bytes.

L

LAN

Local Area Network - the linking of several computers so that they can communicate with each other to form an inter-office or inter-site network within a limited area.

LAN controller

Software and/or hardware which gives a system access to a LAN (networking).

LBS

Location-based Security.

Left Outer Join

An Outer Join in which all the records from the left side of the LEFT JOIN operation in the query's SQL statement are added to the query's results, even if there are no matching values in the joined field from the table on the right. Records from the table on the rre combined with those from the table on the left only when there are matching values in the joined fields.

Library

A file containing previously-developed functions and subroutines that can be used when writing programs.

Listening entry

An entry in the ROUTE-FILE that describes the local system so that the session manager can accept incoming calls (networking).

Live Version of Reality

The live version of Reality is the version that is used automatically when a user logs on to the host. To use a non-live version, use the realroot command to select it.

Local Loopback

A local loopback connection is one that connects back to the same system rather than to a remote entity (networking).

Location-based Security

Location-based security is maintained by means of the SSM utility and saved in the SECURITY file. See also Account-based and User-based security.

Lock Codes

See L/RET and L/UPD.

Locks

Flags set to prevent concurrent access are called locks. Reality uses four types of lock: execution, item, read and update.

Log file

A file used for recording information.

Logoff

To terminate a Reality session.

Logon

To gain initial entry to and begin a Reality session. See also Remote Logon.

Logon Control Program

A program in an account's MD. Whenever a user logs onto this account, the LOGON Processor executes the logon program defined for that user (specified using SSM) or, if none is defined for the user, the logon program for the account (an item in the MD with the same name as the account name or synonym name used to logon). This technique is frequently used to place a user directly into a menu-oriented environment without first having to go through TCL.

An environment option determines the types of command that can be used as logon control programs. The default, is to allow only Procs.

LOGON Message

A message contained in the SYSTEM Dictionary. The default message is' Logon please:'

LOGON Processor

A system subroutine that controls logging onto the database, logging off the database, data access security, and time accounting.

Lost Update

A situation in which Transaction T1 updates an item previously updated, but not committed, by transaction T2, and before T2 can commit, its process aborts. The result is the loss of both updates. This is a transaction management problem that can only occur if item locks are not used correctly within transactions.

LP Scheduler

A UNIX spooler program that controls the lp job request queue, by removing relevant job requests from the queue, passing them on to appropriate printer interface programs for printing and tracking their progress.

LRU

Licensed resource unit. The unit by which a Reality resource is licensed. For example, Web Services are licensed in 1KB data units.

L/RET

Attribute 5 of Account and File Definition Items. This defines the access Retrieval Lock Codes for the account or file defined. A user can only look at files for which his own retrieval codes match that of the file and the account within which it is defined.

LSAP

Link Service Access Point - used to identify services within the link layer (networking).

L/UPD

Attribute 6 of Account and File Definition Items. This defines the access Update Lock Codes for the account or file defined. A user can only update files if his own update codes match that of the file.

M

Macro

A simple batch command formed by combining TCL commands. See TCL macros for details.
An English facility you can use to reduce keyboard input for frequently used database queries. See English Macros for details.

Main Memory

Real, as opposed to virtual, memory. The memory in the physical computer that all data must be read into before any computations can be made on it.

Master Dictionary (MD or M/DICT)

The dictionary file that defines an account. It contains items that point to the code executed by all the TCL commands, to SYSTEM accounts, and to other accounts by means of Q-pointers. The MD also includes all File Definition Items for the account and other items.

MD

See Master Dictionary.

Microprocessor

A CPU on a single chip.

Modifier

A word defined in the MD that modifies the meaning of an English sentence in some particular way.

Modulo

The number of groups allocated to a file. The modulo is used to quickly determine which group contains a particular file item (see Hashing).

For a standard hashed file, the modulo is always the number of groups allocated to the file.
For an automatically sized file, the modulo is the number of groups allocated when the file was created, or a multiple of this value. The actual size of the file depends on the amount by which the file has grown since the modulo last changed. Each time the file doubles in size (full expansion) the modulo is doubled.

MPS

Multi-Protocol Server. A device that allows asynchronous devices such as terminals and printers to be connected to a LAN.

MPTS

Multi-protocol Terminal Server. A device that allows asynchronous devices such as terminals and printers to be connected to a LAN.

Multidrop Line

A single communications line or circuit interconnecting several stations (terminals or printers in different locations).

Multiple Data Sections

Two or more data files defined from a single dictionary.

Multiplex

To interleave or simultaneously transmit two or more messages on a single channel. Messages can be multiplexed in the time domain (called Time Division Multiplexing, or TDM) or in the frequency domain (called Frequency Division Multiplexing, or FDM). Statistical multiplexing is a form of Time Division Multiplexing that optimizes use of the available channel bandwidth.

Multivalue

See Value.

MultiValue System

The generic name for a type of database system that stores information in file items containing delimited data (attributes, values and subvalues, etc.). Reality is one type of MultiValue system.

N

Network: A configuration of two or more interconnected computers and terminals linked to share information and resources.
NETWORK File: A file that provides location-based security information such as CCIs. The PLIds, or partial PLIds, form the item-ids of NETWORK file items.
Network layer: Layer 3 of the OSI Reference Model.
Network user-id: A user-id and password that is used when a local user connects to a remote system. On UNIX hosts, network user-ids are set up in the USERS-FILE on the host. On Windows, they are set up with the SSM Define User Profiles option.
NFT: Network File Transfer.
Node: In tree structures, a point where two or more branches meet.
Normalisation: Minimisation of the duplication of information in a relational database through effective table design.
NSAP: Network Service Access Point – used to identify services within the network layer. NSAPs are used as LAN addresses by OSI full network.
Null network: OSI null network (also known as inactive sub-set). This uses physical addresses.

O

ODBC: Open Database Connectivity. A Microsoft Windows standard protocol for accessing information in SQL database servers which makes applications independent of the database management system from which they derive their data.
ODBC Data Source: An SQL/ODBC connection from a PC to a Reality SQL catalog.
Operating System: A software entity that controls the use of the central processing unit, main memory, and peripheral storage and I/O devices.
Option: A non-mandatory single character (or sequence of single characters) used in a TCL command to qualify the operation of the command in some particular way.
OSI: Open Systems Interconnection - a reference model for communication between systems, devised by the International Standards Organisation (ISO).
Outer Join: A Join in which each matching record from two tables is combined into one record in the query's results. When a record from the table that's contributing all of its records can't be matched with a record from the other table, the record still appears in the results of the query, view, or stored procedure; however, the cells that had no matching record in the other table are empty. You can create three variations of an outer join to specify the unmatched rows to be included: left outer joins, right outer joins and full outer joins.

P

Parallel

A communication method in which all the bits for a byte (or for several bytes) are transmitted at the same time along several channels. Compare with Serial.

Partition Database

A Reality database which is constructed using one or more disk partitions, or files representing disk partitions. It has various advantages over filestore database – see Database Types for details.

Password

An alphanumeric string recognised by the host operating system - that is, UNIX or Windows - which allows you to logon to the system. In addition, an alphanumeric string recognised by Reality which allows you to logon to a database as a particular user or to access a particular account.

PCLINK2

One of the possible “provider types” in the UNIX ROUTE-FILE - PCLINK2 is a software/hardware package for connections to a LAN. It is used on Northgate SX systems.

PCSNI

PC Standard Network Interface. Provides a device-independent network interface for Northgate PCi applications.

PH-HISTORY File

The file that keeps track of all TIPH processes on the system. The PH-STATUS command uses this file to display the current status of TIPH processes. The PH-HISTORY file is held in the SYSFILES account.

PLId

Physical Location Identifier. This identifier uniquely identifies a terminal connected directly or indirectly to a system. The PLId can be assigned a CCI via the NETWORK File. The PLId can be found for the current location using DataBasic SYSTEM(49) function.

Pointer

A data structure that directs an interrogating process to a particular location in the database.

POINTER-FILE

A file that holds saved item lists and cataloged DataBasic programs. A global POINTER-FILE is held in the SYSFILES account. If preferred, this Q-pointer can be replaced with a local file to hold saved item lists; cataloged DataBasic programs, however, are not stored in the local POINTER-FILE.

Port

A physical connection to a computer.
In TCP/IP networks, an endpoint to a logical connection. The port number identifies the type of port – for example, port 80 is used for HTTP.

Primary key

One or more fields (columns) whose value or values uniquely identify each record (row) in an SQL table. A primary key cannot allow Null values and must always have a unique index. A primary key is used to relate a table to foreign keys in other tables. The column(s) defined as the primary key should match the item-id (attribute 0) for the Reality file.

Proc

The Reality procedural processor language. Proc is an interactive language that you can also use to create batch job streams.

PROCLIB

The file used to store Procs that can be accessed by all users. The PROCLIB file is held in the SYSFILES account.

Process

A logical operation connected to a computer or an operating system entity that performs some particular task.

Protocol

The rules for communication between like processes, providing a means to control the orderly communication of information between stations on a data link.

Pseudo-tape

See Tape Image.

Q

QIC: Quarter-Inch Cartridge, a standard for magnetic tape drives.
Q-pointer: An Account or File Synonym Definition Item. Q-pointers allow users to address information in accounts other than the one they are currently logged onto or in files for which they otherwise are not allowed access.
Queue: A group of items arranged in priority sequence in a file on disk or in a buffer waiting for service.

R

R-pointer

An R-pointer is a Remote Account Definition Item.

R/REALLOC

Attribute 13 of Account and File Definition Items. This attribute optionally contains a modulo and separation used to resize and reallocate file space when a user performs a file- or account-restore.

RAM

Random Access Memory. A form of memory storage that a microprocessor (CPU or board controller chip) can address directly and that can be changed rapidly. Compare with ROM.

RCS

Reality Communications Service – software on a UNIX system.

Read Locks

Read locks prevent the occurrence of "soft" group format errors. A read lock specifies that a process is reading from a group. It does not allow updates to the group to occur, but does allow more than one process to read from the same group at the same time.

Reality

A MultiValue database management system.

Reality DR

Reality Disaster Recovery.

Reality SQL Catalog

An SQL catalog consisting of a set of Reality data files and, optionally, indexes which are defined as a set of SQL tables and indexes, and configured to be accessed via an ODBC or JDBC client-server interface. The data is accessed by issuing SQL retrieval and update instructions to an SQL server program on the host.

RealityX

An earlier implementation of the Reality Application Support Environment on UNIX.

Record

A logical entity in a standard data processing file. See Item.

Relational Database

A type of database in which information is accessed by its logical attributes rather than by its physical properties. Data in a classical relational database, is stored as tables, with the rows being records (items) and the columns being fields (attributes).

Remote Account Definition Item

An item in the SYSTEM Dictionary to allow logging on to another system in the network.

Remote BASIC

A mechanism by which DataBasic subroutines can be called from a remote system.

Remote Environment

This is a general term that, unless otherwise stated, includes all of the following:

A remote UNIX system.
A remote Series 19 system, running the REALITY operating system.
RealityX, whether running remotely or locally.

Remote Logon

To log onto a system (other than the one you are physically connected to) over a network.

Remote System

A system other than the one you are physically connected to in a network.

Retix

One of the possible “provider types” in the UNIX ROUTE-FILE (networking).

Retrieval Lock Code

See L/RET.

Roll Back

To restore a database to a previous "correct" condition from an archived image. This term applies only to Transaction Handling.

ROM

Acronym for Read-Only Memory. A form of memory storage in which programs are stored permanently and that a microprocessor (CPU or board controller chip) can address directly. Compare with RAM.

ROSI-UNIX

Reality Open Systems Interface to UNIX (networking).

ROUTE-FILE

A file in the /etc directory on a UNIX host containing items that control the routing a particular process will take through a network. Routing control includes destination system names, network addresses, etc. On Windows hosts, this information is held in the Registry.

For Reality external components that use the PC Standard Network Interface for Windows (PCSNI), routing information is held in a file called winsni.ini in the Windows folder.

Row

A row is a set of associated values, one for each column in an SQL table. A row generally describes a single entity, such as an employee or an order.

RSC

Remote Subroutine Call (Remote Basic).

S

SCREENPRO

Reality's screen building processor.

Security

A means by which a user is prevented from accessing some particular machine resource. See Account-based, Location-based and User-based Security.

SECURITY File

The SYSMAN account file that contains security profiles.

Segment Mark

A character used by Reality to separate groups. Reality uses X'FF' (decimal 255) as the segment mark.

Separation

The number of contiguous frames allocated to a group. On current versions of Reality, this is always 1.

Serial

A communication method in which the bits for a byte are transmitted one after another along a single channel. Compare with Parallel.

SeriesX

A Northgate UNIX system.

Server

A process that provides a service to another, client process. On UNIX, server processes are called daemons.

Servlet

A server-side Java program that services HTTP requests and returns HTTP responses.

Session

A process logged onto Reality, either directly or over a network.

Session file

A UNIX-Connect UNIX file which is used by the session manager to record each incoming and outgoing connection established.

Session Manager

A system process in UNIX or Windows, that accepts and performs security checking on incoming calls. The session manager also maintains the event and session logs which are used to record significant events and errors during the processing of incoming/outgoing connections.

SFT

Simple File Transfer. A utility for copying files between UNIX and Reality, or between one UNIX system and another.

Shadow Database

An optional Reality configuration in which two copies of a database are maintained on the same system to improve resilience in the event of a failure. One copy is maintained as the live database to which users can log on. The other is maintained unmounted as a backup copy which must be updated regularly to Shadow the live database.

S-LAN

A Northgate LAN controller for Series 18/19 systems.

SMA

Spectrum Manufacturers Association. A body that defines standards for MultiValue systems (such as Reality).

SMS

Short Message Service. A service for sending short text messages to mobile telephones.

SMTP

Simple Mail Transfer Protocol. A protocol for sending e-mail messages from mail clients to mail servers, and between mail servers.

SNI

An abbreviation for PCSNI.

SOAP

Simple Object Access Protocol. An XML-based messaging protocol that is used to encode the information in Web service requests and responses.

SovereignX

An application which runs on an SX system and emulates a Sovereign operating system.

Spooler

A Reality process that stores and queues jobs before sending them to a printer or tape device.

SQL

Structured Query Language. A database management language that is the established standard for information retrieval from relational databases. SQL is used to formulate queries to databases which support the ODBC or JDBC interface.

SQL Catalog

A set of SQL tables and indexes, configured to be accessed via an ODBC or JDBC client-server interface.

SSM

A utility used to maintain the Reality user- and location-based security system.

Status Byte

Contains bit flags that are interpreted to define the status of a process.

Structured Query Language

See SQL.

Subvalue

A third-order subset of an item; a second-order subset of an attribute; a first-order subset of a value. Subvalues are groupings of value data that share a particular property.

Subvalue Mark

A character used in Reality to separate subvalues. Reality uses X'FC' (decimal character 252) as the subvalue mark.

SX

A Northgate UNIX system.

SYSFILES

An account (not a logon account) that contains system files. The account is accessed via Q-pointers in the SYSMAN or SYSPROG accounts, and via a Q-pointer in a user account that is created automatically when the user account is created.

SYSMAN Account

The SYStem MANager's account. Contains a complete Master Dictionary and Q-pointers to all required SYSFILES and SYSPROG account files. User account deletion is restricted to this account.

SYSPROG Account

The SYStem PROGrammer's account. SYSPROG contains the commands, files, and utilities that are used to manage and maintain your Reality database.

SYSPROG-PL File

The SYSPROG file that contains Procs and DataBasic programs used by Reality, that are restricted to use from the SYSMAN and SYSPROG accounts.

System Delimiter

A character in the range 251 to 255 (X'FB' to X'FF'); these have the following special meanings:

ASCII Code	Meaning
251 (X'FB')	Start of buffer/text mark.
252 (X'FC')	Subvalue mark.
253 (X'FD')	Value mark.
254 (X'FE')	Attribute/field mark.
255 (X'FF')	Segment/item mark.

See Character-oriented Item and Predefined Symbols for how to enter these characters and how they are displayed.

SYSTEM Dictionary

The fundamental dictionary in the hierarchy of Reality dictionaries. SYSTEM points to every account on a database and is unique within a database.

System name

A local name used in the ROUTE-FILE to identify a remote host, database, printer, etc.

SYSTEM-Level File

A file pointed to by the SYSTEM Dictionary. These include DENAT and SYSFILES.

T

Table

In SQL, the fundamental structure of a relational database management system. A table is an object that stores data in records (rows) and fields (columns). The data is usually about a particular category of things, such as employees or orders.

In HTML, a feature that allows authors to arrange data – text, images, etc. – into rows and columns of cells. They are useful for the display of tabular data and also for controlling the layout of a web document.

Tag

In HTML, a direction embedded within a web page. The web browser uses the information inside the HTML tags to decide how to display or otherwise treat the contents of the HTML document.

In XML, a data marker in an XML document. The tags identify the type of data and their arrangement the relationships between data elements. The tags are arranged in a tree structure.

Tape Image

A tape image is an ordinary file or named pipe (UNIX only), which is used to emulate a Reality tape device. This provides a method of saving Reality data to disk.

TCL

Abbreviation for Terminal Control Language. Reality's command language executive processor.

TCL-I

A TCL processor that executes TCL-I commands. TCL-I commands do not require a file-name, but can have option specifications.

TCL-II

A TCL processor that executes TCL-II commands. TCL-II commands require a file-name and item-related information. TCL-II sentences can also have option specifications.

TCL Macro

A simple batch command formed by combining TCL commands. See TCL macros for details.

TCP/IP

Transmission Control Protocol/Internet Protocol (networking).

Telnet

A bi-directional byte-oriented communications facility, which is generally available on UNIX hosts. A Telnet connection is a TCP/IP terminal connection that is used to transmit data with interspersed Telnet control information.

TERMINAL-OBJECT File

The file that contains object code to be downloaded into intelligent terminals for communications tasks.

Terminal Independent Process Handler

A Reality processor that allows you to create batch jobs on your port and then run them on another process, usually one not associated with a port.

Timeout

Part of a DDA CONNECT message which specifies the amount of time within which a connection must be made (networking).

TIPH

See Terminal Independent Process Handler.

TLI

Transport Library Interface -a standard UNIX library used to access transport layer services (networking).

Transaction

A set of related file updates. Users can define the boundaries of a transaction using DataBasic and ALL statements or Proc-based TCL commands. This term applies only to Transaction Handling.

Transaction Handling

The facility to suspend release of item locks within a transaction and to 'roll back' updates within aborted transactions so as to preserve the integrity of the database. This is a standard Reality feature. Transactions are user-defined within application programs.

Transaction Logging

The method for logging (backing up) transactions to the same or another disk. See also FailSafe Database.

Transport layer

Layer 4 of the OSI Reference Model, or the TCP layer on TCP/IP (networking).

Tree Structure

A type of data structure in which each element is attached to one or more elements directly beneath it. The elements are called nodes and the connections between elements, branches. Trees are often called inverted trees because they are normally drawn with the root at the top.

The nodes at the very bottom of an inverted tree (that is, those that have no nodes below them) are called leaf nodes. Other terms used when referring to trees are borrowed from family trees:

The node directly above a node is the parent of that node.
The nodes directly below another node are the children of that node.
Nodes at the same level and with the same parent are siblings.
All the nodes below another node are descendents of that node.
All the nodes above another node are the ancestors of that node.

Triple DES

An encryption method that applies three phases of encryption/decryption to the supplied data using two or three keys. The first phase encrypts with key 1, the second phase decrypts with key 2 and the third phase encrypts with key 3 if specified or with with key 1.

TSAP

Transport Services Access Point – used to identify services within the transport layer (networking).

U

UNIX: Name given to a family of open architecture computer operating systems of which Solaris, AIX and Linux are variants.
Unrepeatable Read: A situation in which one process reads an item while another process is updating that same item. The read operation is said to be "unrepeatable" because the item being examined is no longer identical with the updated item. This problem can only occur when item locks are not correct.
Update Lock Code: See L/UPD.
Update Locks: Update locks prevent processes from setting read or update locks while the process that sets the lock updates a group. Update locks, once set, do not allow reading or updating by another process.
URL: Uniform Resource Locator - a web address.
User-based Security: Access to data and processes determined by Reality user-id. Maintained via the SSM utility and saved in the USERS file.
User Exit: An entry point to a system input or output conversion subroutine. User exits can be executed from English dictionaries, DataBasic programs, and Procs and as TCL commands.
USERS File: Defines each Reality user-id and assigns their default account (if any), security profile, and so on.
USERS-FILE: A UNIX file that contains local user-ids and maps them to network user-ids and associated passwords to facilitate logging to remote environments and increase security.

V

Value: A second-order subset of an item; a first-order subset of an attribute. Values are groupings of attribute data that share a particular property. Values are sometimes referred to as multivalues.
Value Mark: A character used by Reality to separate values. Reality uses X'FD' (decimal character 253, CTRL+] from the terminal) as the value mark.
VBScript: A programming language that allows executable content to be included with web pages. VBScript is supported only by Microsoft Internet Explorer.
V-Code Sublist: Attribute 8 of a File Definition Item. Specifies an attribute, common to all items in the file, that contains a sublist (multivalues).
V/CONV: Attribute 7 of a Data Definition Item. Contains English conversion codes to be performed on the data described by the Data Definition item before output, and (inversely) to values specified in an English sentence.
V/CORR: Attribute 8 of a Data Definition Item. Contains English conversion codes to be performed on the data described by the Data Definition item before sorts/selects. Previously known as the 'correlative'.
V/MAX: Attribute 10 of a Data Definition Item. Contains the specification for the column width in which information is printed for the attribute defined by this Data Definition Item whenever an English report is run against the data.
V/TYP: Attribute 9 of a Data Definition Item. Contains the alignment specification for output for the attribute defined by this Data Definition Item whenever an English report is run against the data.

W

WAN: An acronym for Wide Area Network. A hardware and software mechanism for linking computers, printers, terminals, and workstations over a wide area that allows them to communicate with one another.
Web Server: A program that makes web pages available to web browsers. It exposes the contents of one or more directories on a host system, which then become accessible by means of a web address (URL). A browser communicates with a web server using HTTP.
Web Service: A way of making programming resources available to remote applications, by using a web server to expose subroutines and functions. Web services use standard protocols (HTTP, XML, SOAP and WSDL) to provide a high level of abstraction, thus making it possible to exchange data between systems that might otherwise be completely incompatible. A developer can therefore create applications that use a combination of local code and web services from a variety of sources.
Windows: A Microsoft 32-bit computer operating system for PC workstations and servers.
WinSNI: The Windows component of PCSNI.
Winsock: Windows Sockets library.
Wrap-up Processor: A system subroutine that terminates a TCL operation by performing disk updates, printing messages as required, and reinitialising functional elements for processing by a subsequent TCL operation.
WSDL: Web Services Description Language. An XML-formatted language used to describe a Web service.

X

X.25: A CCITT standard for synchronous access to packet switched networks. Standard X.25 does not define the communication protocols observed between nodes in a packet switched network.
XML: Extensible Markup Language. The data in an XML document consists of identifying tags, arranged in a tree structure.