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- •Contents
- •Send Us Your Comments
- •Preface
- •Audience
- •Organization
- •Related Documentation
- •Conventions
- •Documentation Accessibility
- •1 Introduction to the Oracle Server
- •Database Structure and Space Management Overview
- •Logical Database Structures
- •Physical Database Structures
- •Data Dictionary Overview
- •Data Access Overview
- •SQL Overview
- •Objects Overview
- •PL/SQL Overview
- •Java Overview
- •XML Overview
- •Transactions Overview
- •Data Integrity Overview
- •SQL*Plus Overview
- •Memory Structure and Processes Overview
- •An Oracle Instance
- •Memory Structures
- •Process Architecture
- •The Program Interface Mechanism
- •An Example of How Oracle Works
- •Application Architecture Overview
- •Client/Server Architecture
- •Multitier Architecture: Application Servers
- •Distributed Databases Overview
- •Replication Overview
- •Streams Overview
- •Advanced Queuing Overview
- •Heterogeneous Services Overview
- •Data Concurrency and Consistency Overview
- •Concurrency
- •Read Consistency
- •Locking Mechanisms
- •Quiesce Database
- •Database Security Overview
- •Security Mechanisms
- •Database Administration Overview
- •Enterprise Manager Overview
- •Database Backup and Recovery Overview
- •Data Warehousing Overview
- •Differences Between Data Warehouse and OLTP Systems
- •Data Warehouse Architecture
- •Materialized Views
- •OLAP Overview
- •Change Data Capture Overview
- •High Availability Overview
- •Transparent Application Failover
- •Online Reorganization Architecture
- •Data Guard Overview
- •LogMiner Overview
- •Real Application Clusters
- •Real Application Clusters Guard
- •Content Management Overview
- •Oracle Internet File System Overview
- •2 Data Blocks, Extents, and Segments
- •Introduction to Data Blocks, Extents, and Segments
- •Data Blocks Overview
- •Data Block Format
- •Free Space Management
- •Extents Overview
- •When Extents Are Allocated
- •Determine the Number and Size of Extents
- •How Extents Are Allocated
- •When Extents Are Deallocated
- •Segments Overview
- •Introduction to Data Segments
- •Introduction to Index Segments
- •Introduction to Temporary Segments
- •Automatic Undo Management
- •3 Tablespaces, Datafiles, and Control Files
- •Introduction to Tablespaces, Datafiles, and Control Files
- •Oracle-Managed Files
- •Allocate More Space for a Database
- •Tablespaces Overview
- •The SYSTEM Tablespace
- •Undo Tablespaces
- •Default Temporary Tablespace
- •Using Multiple Tablespaces
- •Managing Space in Tablespaces
- •Multiple Block Sizes
- •Online and Offline Tablespaces
- •Read-Only Tablespaces
- •Temporary Tablespaces for Sort Operations
- •Transport of Tablespaces Between Databases
- •Datafiles Overview
- •Datafile Contents
- •Size of Datafiles
- •Offline Datafiles
- •Temporary Datafiles
- •Control Files Overview
- •Control File Contents
- •Multiplexed Control Files
- •4 The Data Dictionary
- •Introduction to the Data Dictionary
- •Structure of the Data Dictionary
- •SYS, Owner of the Data Dictionary
- •How the Data Dictionary Is Used
- •How Oracle Uses the Data Dictionary
- •How to Use the Data Dictionary
- •Dynamic Performance Tables
- •Database Object Metadata
- •Introduction to an Oracle Instance
- •The Instance and the Database
- •Connection with Administrator Privileges
- •Initialization Parameter Files
- •Instance and Database Startup
- •How an Instance Is Started
- •How a Database Is Mounted
- •What Happens When You Open a Database
- •Database and Instance Shutdown
- •Close a Database
- •Unmount a Database
- •Shut Down an Instance
- •6 Application Architecture
- •Client/Server Architecture
- •Multitier Architecture
- •Clients
- •Application Servers
- •Database Servers
- •Oracle Net Services
- •How Oracle Net Services Works
- •The Listener
- •7 Memory Architecture
- •Introduction to Oracle Memory Structures
- •System Global Area (SGA) Overview
- •Dynamic SGA
- •Database Buffer Cache
- •Redo Log Buffer
- •Shared Pool
- •Large Pool
- •Control of the SGA’s Use of Memory
- •Other SGA Initialization Parameters
- •Program Global Areas (PGA) Overview
- •Content of the PGA
- •SQL Work Areas
- •PGA Memory Management for Dedicated Mode
- •Dedicated and Shared Servers
- •Software Code Areas
- •8 Process Architecture
- •Introduction to Processes
- •Multiple-Process Oracle Systems
- •Types of Processes
- •User Processes Overview
- •Connections and Sessions
- •Oracle Processes Overview
- •Server Processes
- •Background Processes
- •Trace Files and the Alert Log
- •Shared Server Architecture
- •Scalability
- •Dispatcher Request and Response Queues
- •Shared Server Processes (Snnn)
- •Restricted Operations of the Shared Server
- •Dedicated Server Configuration
- •The Program Interface
- •Program Interface Structure
- •Program Interface Drivers
- •Communications Software for the Operating System
- •9 Database Resource Management
- •Introduction to the Database Resource Manager
- •Database Resource Manager Overview
- •Example of a Simple Resource Plan
- •How the Database Resource Manager Works
- •Resource Control
- •Database Integration
- •Performance Overhead
- •Resource Plans and Resource Consumer Groups
- •Activation of a Resource Plan
- •Groups of Resource Plans
- •Resource Allocation Methods and Resource Plan Directives
- •Resource Plan Directives
- •CPU Resource Allocation
- •Interaction with Operating-System Resource Control
- •Dynamic Reconfiguration
- •10 Schema Objects
- •Introduction to Schema Objects
- •Tables
- •How Table Data Is Stored
- •Nulls Indicate Absence of Value
- •Default Values for Columns
- •Partitioned Tables
- •Nested Tables
- •Temporary Tables
- •External Tables
- •Views
- •How Views are Stored
- •How Views Are Used
- •Mechanics of Views
- •Dependencies and Views
- •Updatable Join Views
- •Object Views
- •Inline Views
- •Materialized Views
- •Define Constraints on Views
- •Refresh Materialized Views
- •Materialized View Logs
- •Dimensions
- •The Sequence Generator
- •Synonyms
- •Indexes
- •Unique and Nonunique Indexes
- •Composite Indexes
- •Indexes and Keys
- •Indexes and Nulls
- •Function-Based Indexes
- •How Indexes Are Stored
- •How Indexes Are Searched
- •Key Compression
- •Reverse Key Indexes
- •Bitmap Indexes
- •Bitmap Join Indexes
- •Index-Organized Tables
- •Benefits of Index-Organized Tables
- •Index-Organized Tables with Row Overflow Area
- •Secondary Indexes on Index-Organized Tables
- •Bitmap Indexes on Index-Organized Tables
- •Partitioned Index-Organized Tables
- •Index-Organized Table Applications
- •Application Domain Indexes
- •Clusters
- •Hash Clusters
- •Introduction to Partitioning
- •Partition Key
- •Partitioned Tables
- •Partitioned Index-Organized Tables
- •Partitioning Methods
- •Range Partitioning
- •List Partitioning
- •Hash Partitioning
- •Composite Partitioning
- •When to Partition a Table
- •Partitioned Indexes
- •Local Partitioned Indexes
- •Global Partitioned Indexes
- •Global Nonpartitioned Indexes
- •Partitioned Index Examples
- •Miscellaneous Information about Creating Indexes on Partitioned Tables
- •Using Partitioned Indexes in OLTP Applications
- •Using Partitioned Indexes in Data Warehousing and DSS Applications
- •Partitioned Indexes on Composite Partitions
- •Partitioning to Improve Performance
- •Partition Pruning
- •Partition-wise Joins
- •Parallel DML
- •Introduction to Oracle Datatypes
- •Character Datatypes
- •CHAR Datatype
- •VARCHAR2 and VARCHAR Datatypes
- •Length Semantics for Character Datatypes
- •NCHAR and NVARCHAR2 Datatypes
- •Use of Unicode Data in an Oracle Database
- •LOB Character Datatypes
- •LONG Datatype
- •NUMBER Datatype
- •Internal Numeric Format
- •DATE Datatype
- •Use of Julian Dates
- •Date Arithmetic
- •Centuries and the Year 2000
- •Daylight Savings Support
- •Time Zones
- •LOB Datatypes
- •BLOB Datatype
- •CLOB and NCLOB Datatypes
- •BFILE Datatype
- •RAW and LONG RAW Datatypes
- •ROWID and UROWID Datatypes
- •The ROWID Pseudocolumn
- •Physical Rowids
- •Logical Rowids
- •Rowids in Non-Oracle Databases
- •ANSI, DB2, and SQL/DS Datatypes
- •XML Datatypes
- •XMLType Datatype
- •URI Datatypes
- •Data Conversion
- •13 Object Datatypes and Object Views
- •Introduction to Object Datatypes
- •Complex Data Models
- •Multimedia Datatypes
- •Object Datatype Categories
- •Object Types
- •Collection Types
- •Type Inheritance
- •FINAL and NOT FINAL Types
- •NOT INSTANTIABLE Types and Methods
- •User-Defined Aggregate Functions
- •Why Have User-Defined Aggregate Functions?
- •Creation and Use of UDAGs
- •How Do Aggregate Functions Work?
- •Application Interfaces
- •JPublisher
- •JDBC
- •SQLJ
- •Datatype Evolution
- •Introduction to Object Views
- •Advantages of Object Views
- •How Object Views Are Defined
- •Use of Object Views
- •Updates of Object Views
- •Updates of Nested Table Columns in Views
- •View Hierarchies
- •14 SQL, PL/SQL, and Java
- •SQL Overview
- •SQL Statements
- •Identification of Nonstandard SQL
- •Recursive SQL
- •Cursors
- •Shared SQL
- •Parsing
- •SQL Processing
- •The Optimizer Overview
- •PL/SQL Overview
- •How PL/SQL Runs
- •Language Constructs for PL/SQL
- •PL/SQL Program Units
- •PL/SQL Collections and Records
- •PL/SQL Server Pages
- •Java Overview
- •Java and Object-Oriented Programming Terminology
- •Class Hierarchy
- •Interfaces
- •Polymorphism
- •The Java Virtual Machine (JVM)
- •Why Use Java in Oracle?
- •Oracle’s Java Application Strategy
- •15 Dependencies Among Schema Objects
- •Introduction to Dependency Issues
- •Resolution of Schema Object Dependencies
- •Compilation of Views and PL/SQL Program Units
- •Function-Based Index Dependencies
- •Object Name Resolution
- •Shared SQL Dependency Management
- •Local and Remote Dependency Management
- •Management of Local Dependencies
- •Management of Remote Dependencies
- •16 Transaction Management
- •Introduction to Transactions
- •Statement Execution and Transaction Control
- •Statement-Level Rollback
- •Resumable Space Allocation
- •Transaction Management Overview
- •Commit Transactions
- •Rollback of Transactions
- •Savepoints In Transactions
- •Transaction Naming
- •The Two-Phase Commit Mechanism
- •Discrete Transaction Management
- •Autonomous Transactions
- •Autonomous PL/SQL Blocks
- •Transaction Control Statements in Autonomous Blocks
- •17 Triggers
- •Introduction to Triggers
- •How Triggers Are Used
- •Parts of a Trigger
- •The Triggering Event or Statement
- •Trigger Restriction
- •Trigger Action
- •Types of Triggers
- •Row Triggers and Statement Triggers
- •BEFORE and AFTER Triggers
- •INSTEAD OF Triggers
- •Triggers on System Events and User Events
- •Trigger Execution
- •The Execution Model for Triggers and Integrity Constraint Checking
- •Data Access for Triggers
- •Storage of PL/SQL Triggers
- •Execution of Triggers
- •Dependency Maintenance for Triggers
- •18 Parallel Execution of SQL Statements
- •Introduction to Parallel Execution
- •When to Implement Parallel Execution
- •When Not to Implement Parallel Execution
- •How Parallel Execution Works
- •Parallelized SQL Statements
- •Degree of Parallelism
- •SQL Operations That Can Be Parallelized
- •Parallel Query
- •Parallel DDL
- •Parallel DML
- •SQL*Loader
- •How to Make a Statement Run in Parallel
- •19 Direct-Path INSERT
- •Introduction to Direct-Path INSERT
- •Advantages of Direct-Path INSERT
- •Serial and Parallel Direct-Path INSERT
- •Direct-Path INSERT Into Partitioned and Nonpartitioned Tables
- •Serial Direct-Path INSERT into Partitioned and Nonpartitioned Tables
- •Parallel Direct-Path INSERT into Partitioned Tables
- •Parallel Direct-Path INSERT into Nonpartitioned Tables
- •Direct-Path INSERT and Logging Mode
- •Direct-Path INSERT with Logging
- •Direct-Path INSERT without Logging
- •Additional Considerations for Direct-Path INSERT
- •Index Maintenance with Direct-Path INSERT
- •Space Considerations with Direct-Path INSERT
- •Locking Considerations with Direct-Path INSERT
- •20 Data Concurrency and Consistency
- •Introduction to Data Concurrency and Consistency in a Multiuser Environment
- •Preventable Phenomena and Transaction Isolation Levels
- •Overview of Locking Mechanisms
- •How Oracle Manages Data Concurrency and Consistency
- •Multiversion Concurrency Control
- •Statement-Level Read Consistency
- •Transaction-Level Read Consistency
- •Read Consistency with Real Application Clusters
- •Oracle Isolation Levels
- •Comparison of Read Committed and Serializable Isolation
- •Choice of Isolation Level
- •How Oracle Locks Data
- •Transactions and Data Concurrency
- •Deadlocks
- •Types of Locks
- •DML Locks
- •DDL Locks
- •Latches and Internal Locks
- •Explicit (Manual) Data Locking
- •Oracle Lock Management Services
- •Flashback Query
- •Flashback Query Benefits
- •Some Uses of Flashback Query
- •21 Data Integrity
- •Introduction to Data Integrity
- •Types of Data Integrity
- •How Oracle Enforces Data Integrity
- •Introduction to Integrity Constraints
- •Advantages of Integrity Constraints
- •The Performance Cost of Integrity Constraints
- •Types of Integrity Constraints
- •NOT NULL Integrity Constraints
- •UNIQUE Key Integrity Constraints
- •PRIMARY KEY Integrity Constraints
- •Referential Integrity Constraints
- •CHECK Integrity Constraints
- •The Mechanisms of Constraint Checking
- •Default Column Values and Integrity Constraint Checking
- •Deferred Constraint Checking
- •Constraint Attributes
- •SET CONSTRAINTS Mode
- •Unique Constraints and Indexes
- •Constraint States
- •Constraint State Modification
- •22 Controlling Database Access
- •Introduction to Database Security
- •Schemas, Database Users, and Security Domains
- •User Authentication
- •Authentication by the Operating System
- •Authentication by the Network
- •Authentication by the Oracle Database
- •Multitier Authentication and Authorization
- •Authentication by the Secure Socket Layer Protocol
- •Authentication of Database Administrators
- •Oracle Internet Directory
- •User Tablespace Settings and Quotas
- •Default Tablespace Option
- •Temporary Tablespace Option
- •Tablespace Access and Quotas
- •The User Group PUBLIC
- •User Resource Limits and Profiles
- •Types of System Resources and Limits
- •Profiles
- •23 Privileges, Roles, and Security Policies
- •Introduction to Privileges
- •System Privileges
- •Schema Object Privileges
- •Table Security
- •View Security
- •Procedure Security
- •Type Security
- •Introduction to Roles
- •Common Uses for Roles
- •The Mechanisms of Roles
- •Grant and Revoke Roles
- •Who Can Grant or Revoke Roles?
- •Role Names
- •Security Domains of Roles and Users
- •PL/SQL Blocks and Roles
- •Data Definition Language Statements and Roles
- •Predefined Roles
- •The Operating System and Roles
- •Roles in a Distributed Environment
- •Fine-Grained Access Control
- •Dynamic Predicates
- •Application Context
- •Secure Application Roles
- •Creation of Secure Application Roles
- •24 Auditing
- •Introduction to Auditing
- •Features of Auditing
- •Mechanisms for Auditing
- •Statement Auditing
- •Privilege Auditing
- •Schema Object Auditing
- •Schema Object Audit Options for Views and Procedures
- •Fine-Grained Auditing
- •Focus Statement, Privilege, and Schema Object Auditing
- •Successful and Unsuccessful Statement Executions Auditing
- •BY SESSION and BY ACCESS Clauses of Audit Statement
- •Audit By User
- •Audit in a Multitier Environment
- •Allocating Extents in Dictionary Managed Tablespaces
- •Introduction to Rollback Segments
- •PCTFREE, PCTUSED, and Row Chaining
- •Glossary
- •Index
2
Data Blocks, Extents, and Segments
This chapter describes the nature of and relationships among the logical storage structures in the Oracle server. It includes:
Introduction to Data Blocks, Extents, and Segments
Data Blocks Overview
Extents Overview
Segments Overview
Data Blocks, Extents, and Segments 2-1
Introduction to Data Blocks, Extents, and Segments
Introduction to Data Blocks, Extents, and Segments
Oracle allocates logical database space for all data in a database. The units of database space allocation are data blocks, extents, and segments. Figure 2–1 shows the relationships among these data structures:
Figure 2–1 The Relationships Among Segments, Extents, and Data Blocks
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Data Blocks
At the finest level of granularity, Oracle stores data in data blocks (also called logical blocks, Oracle blocks, or pages). One data block corresponds to a specific number of bytes of physical database space on disk.
The next level of logical database space is an extent. An extent is a specific number of contiguous data blocks allocated for storing a specific type of information.
2-2 Oracle9i Database Concepts
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