Glossary - Visual Explain

Teradata Visual Explain User Guide

Product
Visual Explain
Release Number
15.10
Language
English (United States)
Last Update
2018-10-07
dita:id
B035-2504
lifecycle
previous
Product Category
Teradata Tools and Utilities

A

administrator

A special user responsible for allocating resources to a community of users.

access right

In Teradata SQL, a user’s right to perform the Teradata SQL statements granted to the user against a table, database, user, macro, or view. Also known as a privilege.

AMP

Access Module Processor. A virtual processor that receives steps from a PE and performs database functions to retrieve or update data. Each AMP is associated with one virtual disk, where the data is stored. An AMP manages only its own virtual disk and not the virtual disk of any other AMP.

B

Basic Teradata Query

See BTEQ.

BTEQ

Basic Teradata Query. Command-based application that enables users on a workstation to communicate with one or more Teradata Database systems.

C

Call-Level Interface, version 2

See CLIv2

candidate index column

A column for which the value or join‑range access frequencies stored in the Field table of the specified QCD are greater than 0.

cardinality

In set theory, cardinality refers to the number of members in the set. When specifically applied to database theory, the cardinality of a table refers to the number of rows contained in a table.

CLIv2

Call‑Level Interface, version 2. A programming interface designed to support SQL access to databases from shrink-wrapped application programs. SQL/CLI provides an international‑standard, implementation‑independent CLI to access SQL databases. Client‑server tools can easily access a database through DLLs. It supports and encourages a rich set of client‑server tools.

column

In the relational model of Teradata SQL, databases consist of one or more tables. In turn, each table consists of fields, organized into one or more columns by zero or more rows. All of the fields of a given column share the same attributes.

cost

The outlay of database resources used by a given query.

D

database

A related set of tables that share a common space allocation and owner. A collection of objects that provide a logical grouping for information. The objects include tables, views, macros, triggers, and stored procedures. See also table.

Database Administrator

See DBA.

Database Query Log

See DBQL.

data definition

The statements and facilities that manipulate database structures and the Data Dictionary information kept about these structures. These statements include CREATE, DROP, ALTER, and MODIFY.

Data Definition Language

See DDL.

Data Dictionary

In Teradata Database, the information automatically maintained about all tables, views, macros, databases, and users known to the Teradata Database system. The dictionary includes information about ownership, space allocation, accounting, and access right relationships between those objects. Data Dictionary information is updated automatically during the processing of Teradata SQL data definition statements. The parser uses the Data Dictionary information to obtain information needed to process all Teradata SQL statements.

Data Manipulation Language

See DML.

DBA

Database Administrator.

DBQL

Database Query Log. A set of measures that can be analyzed over a period of time to verify system usage or to more closely examine a query that uses a large amount of valuable system resources.

DDL

Data Definition Language. In Teradata SQL, the statements and facilities that manipulate database structures (such as CREATE, MODIFY, DROP, GRANT, REVOKE, and GIVE) and the dictionary information kept about those structures. In the typical, pre‑relational data management system, data definition and data manipulation facilities are separated. The data‑definition facilities are less flexible and more difficult to use than in a relational system.

DML

Data Manipulation Language. In Teradata SQL, the statements and facilities that manipulate or change the information content of the database. These statements include INSERT, UPDATE, and DELETE.

domain name

A group of computers whose hostnames (the unique name by which a computer is known on a network) share a common suffix (the domain name).

F

field

The basic unit of information stored in a Teradata Database. A field is either null or has a single numeric or string value.

G

GDO

Globally Distributed Object. A data structure that is shared by all of the virtual processors in Teradata Database configuration.

Globally Distributed Object

See GDO.

H

hash-ordered secondary index

See HOSI.

HOSI

hash‑ordered secondary index. A secondary index whose rows are ordered by hash.

I

index candidate

See candidate index column.

J

join

A select operation that combines information from two or more tables to produce a result.

L

log

A record of events. A file that records events. Many programs produce log files. Review a log file to assist in determining what is happening when problems occur. Log files use the extension .log.

M

macro

A set of Teradata SQL statements stored by a Teradata Database and executed by a single EXECUTE statement. Each macro execution is implicitly treated as a transaction.

N

name

A user‑supplied word that refers to an object, such as column, database, macro, table, user, or view.

non-unique secondary index

See NUSI.

null

The absence of a value for a field.

NUSI

non‑unique secondary index. One of two types of secondary indexes. A secondary index can be specified at table creation or at any time during the life of the table. The index can consist of up to 16 columns. To get the benefit of the index, the query has to specify a value for all columns in the secondary index. A NUSI is usually specified in order to prevent full-table scans.

O

object

In object‑oriented programming, a unique instance of a data structure defined according to the template provided by its class. Each object has its own values for the variables belonging to its class and can respond to the messages, or methods, defined by its class.

object definition

The details of the structure and instances of the objects used by a given query. Object definitions are used to create the tables, views, macros, triggers, join indexes, and stored procedures in a database.

ODBC

Open Database Connectivity. Under ODBC, drivers are used to connect applications with databases. The ODBC driver processes ODBC calls from an application, but passes SQL requests to Teradata Database for processing.

Open Database Connectivity

See ODBC.

P

parameter

A variable name in a macro for which an argument value is substituted when the macro is executed.

parser

A program executing in a parsing engine that translates Teradata SQL statements entered by a user into the steps that accomplish the user’s intensions.

Parsing Engine

See PE.

PE

Parsing Engine. An instance (virtual processor) of the database management session control, parsing, and dispatching processes and their data context (caches).

privilege

See access right.

production system

A Teradata Database used in a live environment at a customer site. A system that is actively used for day‑to‑day business operations. This differs from a test or development system that is used to create new queries or test new features before using them on the production system.

Q

QCD

Query Capture Database. A database of relational tables that store the steps of any query plan captured by the QCF.

QCF

Query Capture Facility. Provides a method to capture and store the steps from any query plan in a set of predefined relational tables called the QCD.

query

A Teradata SQL statement, such as a SELECT statement.

Query Capture Database

See QCD.

Query Capture Facility

See QCF.

R

random AMP sample

An arbitrary sample from an AMP. These are samples of the tables in a query or all of the tables in a given database.

recursive query

A named query expression that is allowed to reference itself in its own definition, giving the user a simple way to specify a search of a table using iterative self‑join and set operations. Use a recursive query to query hierarchies of data. Hierarchical data could be organizational structures such as department and sub-department, forums of discussions such as posting, response, and response to response, bill of materials, and document hierarchies.

Relational Database Management System

A database management system in which complex data structures are represented as simple two‑dimensional tables consisting of columns and rows.

request

In host software, a message sent from an application program to Teradata Database.

result

The information returned to the user to satisfy a request made of Teradata Database.

row

The fields that represent one entry under each column in a table. The row is the smallest unit of information operated on by data manipulation statements.

S

session

In client software, a logical connection between an application program on a host and Teradata Database. The session permits the application program to send one request to and receive one response from Teradata Database at a time.

SQL

Structured Query Language. A standardized query language for requesting information from a database. SQL consists of a set of facilities for defining, manipulating, and controlling data in a relational database.

statement

A request for processing by Teradata Database that consists of a keyword verb, optional phrases, and operands. The statement is processed as a single entity.

statistics

These are the details of the processes used to collect, analyze, and transform the database objects used by a given query.

stored procedure

Combinations of procedural and non‑procedural statements run using a single call statement.

Structured Query Language

See SQL.

T

table

A two‑dimensional structure made up of one or more columns with zero or more rows that consist of fields of related information. See also database.

Target Level Emulation

See TLE.

TDPid

Teradata Director Program ID. Assigned by the system administrator.

Teradata Director Program ID

See TDPid.

TLE

Target Level Emulation. Emulate a target environment (target system) by capturing system-level information from that environment. The captured information is stored in the relational tables SystemFE.Opt_Cost_Table and SystemFE.Opt_RAS_Table. The information in these tables can be used on a test system with the appropriate column and indexes to make the Optimizer generate query plans as if it were operating in the target system rather than the test system.

trigger

One or more Teradata SQL statements associated with a table and executed when specified conditions are met.

U

user

A database associated with a person who uses the Teradata Database. The database stores the person’s private information and accesses other Teradata Databases.

Unicode®, UTF-8, and UTF-16 character sets

UTF-8 and UTF-16 are two of the standard ways of encoding Unicode® character data. The Teradata Database supports UTF-8 and UTF-16 client character sets. The UTF-8 client character set supports UTF-8 encoding. The Teradata Database supports UTF-8 characters that can consist of from one to three bytes. The UTF-16 client character set supports UTF-16 encoding. The Teradata Database supports the Unicode® 6.0 standard, where each defined character requires exactly 16 bits. There are restrictions imposed by the Teradata Database on using the UTF-8 and UTF-16 character sets. For details, see International Character Set Support (B035-1125).

unique secondary index

See USI.

USI

unique secondary index. One of two types of secondary indexes. A secondary index can be specified at table creation or at any time during the life of the table. It can consist of up to 16 columns. To get the benefit of the index, the query has to specify a value for all columns in the secondary index. A USI has two purposes: to speed up access to a row that otherwise might require a full table scan without having to reply on the primary index, and to enforce uniqueness of a column or set of columns.

V

value-ordered secondary index

See VOSI.

view

An alternate way of organizing and presenting information in Teradata Database. A view, like a table, has rows and columns. However, the rows and columns of a view are not directly stored by Teradata Database. They are derived from the rows and columns of tables (or other views) whenever the view is referenced.

VOSI

value‑ordered secondary index. A NUSI can be value ordered which means the NUSI can be sorted on the key values themselves rather than on the corresponding hash codes. This is useful for range queries where only a portion of the index subtable will be accessed. With a value-ordered NUSI, only those blocks in the NUSI subtable that are within the range are scanned. It must be a number value, up to 4 b, versus a longer character column. DATE is the most commonly used data type. The actual data value is stored as part of the NUSI structure.