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Introduction to the Teradata® RDBMS for UNIX® Version 2 Release 2.1 - NCR

NCR Introduction to the Teradata® RDBMS for UNIX® Version 2 Release 2.1 - NCR, 1998. - 315 p.
Download (direct link): inntroduktionteradata1998.pdf
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Each type of vproc is described in the following passages.

Each Parsing Engine (PE) executes the database software that manages sessions and decomposes SQL into parallel steps.

The software, as shown in Figure 2-1, consists of the following elements:

• Parser (including the Optimizer)

• Dispatcher

• Session Control

The Parser decomposes the SQL into relational data management processing steps.

Introduction to the Teradata RDBMS for UNIX

2-9
Teradata RDBMS Architecture

Virtual Processors

Figure 2-1 PE Software Components

AMPs

Figure 2-2 AMP Software Components

The steps are passed to the Dispatcher, which sends the steps to the appropriate AMPs.

Session Control provides user session management such as establishing and terminating sessions.

Parser (including Optimizer) Session Control
Dispatcher
PDE
UNIX

GG01A029

Each Access Module Process (AMP) executes the database software that performs relational functions and data management.

Each AMP, as shown in Figure 2-2, is assigned a portion of the database to control.

Each AMP provides the following functions:

• Data access

• Concurrency control

• Journaling

• Cache management

• Recovery functions.

Each AMP maintains its portion of the database tables stored on disks.

Relational Database Management File System/Data Management PDE UNIX

GG01A028

2-10

Introduction to the Teradata RDBMS for UNIX
Teradata RDBMS Architecture

The Parsing Engine

The Parsing Engine

The Parsing Engine is the processor that communicates with the Introduction 2 client system on one side and with the AMPs (via the BYNET or

Vnet) on the other.

Each PE executes the database software that manages sessions, decomposes SQL statements into parallel steps, and returns the answer rows to the requesting client.

The major components of the PE are

• Session Control

• SQL Parser

• Dispatcher.

The client interface provides handshaking across the Oient Interface communications channel between the server and its client or clients.

For a mainframe link, the connection is made by means of either:

• Serial (ESCON)

• Parallel (Bus & Tag) Channel

implemented by means of the Teradata Channel Interface (TCI) protocol handler.

In the case of a network link, the connection is by means of a LAN connection using either:

• TCP/IP

• ISO/OSI protocols

implemented by means of the Teradata Gateway.

Session numbers are assigned by the TDP and communicated to the Session Control 2 server.

The PE establishes a session only if it can validate the username, password, and user type (application program, interactive BTEQ terminal, or third party software product). All subsequent traffic for the session are identified by their host id, session number, and request number.

Introduction to the Teradata RDBMS for UNIX

2-11
Teradata RDBMS Architecture

The Parsing Engine

The Teradata RDBMS is an ASCII machine. The parsing engine Input Data Conversion converts EBCDIC (and other non-ASCII) input to ASCII before

processing it.

2-12

Introduction to the Teradata RDBMS for UNIX
Teradata RDBMS Architecture

The Parsing Engine

SQL Parser

2 The Syntaxer checks the syntax of an incoming request.
IF there are . . . THEN the Syntaxer . . .
no errors converts the request to a parse tree and passes it to the Resolver.
errors passes an error message back to the requestor.

3 The Resolver adds information from the Data Dictionary cache to convert database, table, view, and macro names to numeric identifiers, then produces lists of objects and access rights. The output is a Resolver tree, which the Resolver passes to a security checking mechanism.
4 The security module checks access rights in the Data Dictionary.
IF the access rights are . . . THEN the Security module . . .
valid passes the request to the Optimizer.
not valid aborts the request.

5 The Optimizer determines the most effective way to access the data needed by the request.
6 The Optimizer scans the request to determine where locks should be placed, then passes the optimized parse tree to the Generator.

The SQL parser handles all incoming SQL requests. It processes these requests as follows.

Stage

Process

The Parser looks in the Request cache to determine if the request is already there.

IF the request is . . . THEN the Parser . . .
in the Request cache generates AMP steps and passes them to the gncApply software.
not in the Request cache begins processing the request with the Syntaxer.

1

Introduction to the Teradata RDBMS for UNIX

2-13
Teradata RDBMS Architecture

The Parsing Engine

The Dispatcher

Stage Process
7 The Generator transforms the optimized parse tree into plastic steps and passes them to the gncApply software. Plastic steps are directives to the database management system that do not contain data values
8 gncApply takes the plastic steps produced by the Generator and transforms them into concrete steps. Concrete steps are directives to the database management system that contain user- and session-specific information as well as data parcels.
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