Oracle Database 12c Fundamentals

Exploring the Oracle Database 12c Architecture: Part 1

Timothy Warnertimwarnertech.com

@TechTrainerTim

Overview: Exploring the Oracle Database 12c Architecture Part 1/1

Goals of this course and learning path

What is Oracle Database 12c?

Understanding Oracle client/server architecture

Understanding Oracle Database 12c memory structures

Goals of this Course and Learning Path

Students come from a variety of backgrounds: New to databases

New to Oracle (previous experience with other platforms)

New to Oracle Database 12c

Oracle Certified Associate (OCA) learning path: Oracle Database 12c Fundamentals

Oracle Database 12c Installation and Upgrade

Oracle Database 12c Disaster Recovery and Data Movement

Get familiar with Oracle University (education.oracle.com)

What is Oracle Database 12c?

A database is an organized collection of data that is treated as a unit

A relational database management system (RDBMS) is the infrastructure that supports multi-user database access Secure data storage, quick retrieval by using SQL

Oracle is called an object-relational database

EF “Ted” Codd (1923-2003)

Key terms in relational theory: Relation = table

Attribute = column

Tuple = row

A Bit of Oracle Version History

Oracle v1 written but never officially released in 1978

Oracle 8i released in 1999 (i = Internet)

Oracle 10g released in 2003 (g = grid computing)

Oracle 12c released in 2014 (c = cloud)

Understanding Oracle Client/Server Architecture

Client (not the user): application that communicates either through a middle-tier (middleware) application or directly with Oracle server

Middle tier: Homegrown LOB, Oracle Fusion Applications/Middleware HTTP(S) Web server

Oracle Database itself comprises the “back end” storage tier Although the platform is capable of declarative/procedural logic

Oracle Exadata Database Machine

Database and Instance

Instance: Shared memory area (system global area, or SGA) and background processes

Database: Set of files, located on disk, that store data Data files, ORL files, control files, etc.

Single instance vs. clustered (grid) instance: Cluster involves several instances that access shared storage and a single

database in an active/active configuration

Multitenant Architecture (New in 12c!) Container database (CDB) with multiple pluggable databases (PDBs)

Provides hardware cost reduction, easier management/monitoring

Updates and maintenance can be performed just once on the CDB

Oracle Database 12c Memory Structures

System Global Area (SGA): Group of shared memory structures that store data and manage information for a single database instance

Program Global Area (PGA): Stores data and manages information for a server process or background process

System Global Area (SGA) Components

Database buffer cache: Stores copies of data blocks read from data files and waiting to be written to data files

Redo log buffer: Circular buffer that stores all changes made to the DB (can reconstruct DDL or DML operations)

Shared pool: “Catch all” bucket: Shared SQL, Data Dictionary cache, etc.

Large pool: Stores memory allocations that are larger than the shared pool can handle (overflow)

Java pool: Stores session-specific Java code within the JVM

Streams pool: Used in Oracle Streams database replication

Fixed SGA: Internal housekeeping area (locks, processes, etc.)

Program Global Area (PGA) Components

File clerk/countertop analogy for understanding the server process and the PGA

Session memory: logon information and session-related data

Private SQL area: Query execution work data

Restricting the PGA size (new in 12c!) PGA_AGGREGATE_LIMIT initialization parameter

Managing Memory in Oracle Database 12c

Automatic Memory Management MEMORY_TARGET initialization parameter

Automatic or Manual Shared Memory Management Pertains to the SGA

Automatic or Manual PGA Memory Management

Summary

Oracle Database is the back-end storage tier in a typical multi-tier client/server application architecture

An Oracle “database” actually consists of two parts: the instance and the database files

An Oracle instance consists of several memory structures and background processes SGA

PGA

The Oracle database, proper, consists of the file system objects Logical vs. physical distinction is a big deal with Oracle products