1 Oracle Data Guard: Overview
After completing this lesson, you should be able to do the following:
Describe the factors that affect planned and unplanned downtime
Describe the basic components of Oracle Data Guard
Explain the differences between physical and logical standby databases
Explain the benefits of creating a Data Guard environment
Explain the use of Data Guard in high-availability architectures
1
Oracle Data Guard: Overview
Copyright © 2006, Oracle. All rights reserved.
Objectives
After completing this lesson, you should be able to do the
following:
• Describe the factors that affect planned and unplanned
downtime
• Describe the basic components of Oracle Data Guard
• Explain the differences between physical and logical
standby databases
• Explain the benefits of creating a Data Guard
environment
• Explain the use of Data Guard in high-availability
architectures
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Causes of Data Loss
Hardware & system errors 49%
Human errors 36%
Computer viruses 7%
Software corruption 4%
Natural disasters 3%
Source: Disaster Recovery Journal
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Understanding the Causes of Downtime
Storage
failure
Computer
failures
Unplanned Human
downtime error
Data
failures
Corruption
Data Site
changes failure
Planned
downtime
System
changes
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What Is Oracle Data Guard?
Primary Standby
database Redo transport database
Oracle Net
Database Database
copy
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Types of Standby Databases
There are two types of standby databases:
• Physical standby database
– Identical to the primary database on a block-for-block
basis
– Synchronized with the primary database through
application of redo data received from the primary
database
• Logical standby database
– Shares the same schema definition
– Synchronized with the primary database by transforming
the data in the redo received from the primary database
into SQL statements and then executing the SQL
statements
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Oracle Data Guard Broker Framework
Oracle
Management
Server
Repository
Agent Agent
Primary Standby
database database
Data Data
Guard Guard
broker Enterprise Manager broker
CLI management client
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Types of Services
There are three types of services provided with Data Guard:
• Redo transport services
• Log apply services
– Redo Apply
– SQL Apply
• Role-management services
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Role Transitions: Switchover and Failover
• Oracle Data Guard supports two role-transition
operations:
– Switchover
—
Planned role reversal
—
Used for OS or hardware maintenance
– Failover
—
Unplanned role reversal
—
Use in emergency
—
Zero or minimal data loss depending on choice
of data protection mode
—
Can be initiated automatically when fast-start failover is
enabled
• Role-transition operations are not automatically invoked.
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Data Protection Modes
• Maximum protection
• Maximum availability
• Maximum performance
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Benefits of Implementing
Oracle Data Guard
Oracle Data Guard provides the following benefits:
• Continuous service through disasters or crippling data
failures
• Complete data protection against corruptions and data
loss
• Efficient use of system resources
• Elimination of idle standby systems
• Flexible configuration of your system to meet business
protection and recovery requirements
• Centralized management
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Role of Data Guard in a
High-Availability Architecture
Computer RAC
failures
Storage
failure
ASM
Human Flashback
error technology
Data
failures
Oracle HARD
Corruption RMAN
Site
Data Guard
failure
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Role of Data Guard in a
High-Availability Architecture
• Online schema and
data reorganization
Data • Partitioned tables
changes and indexes
• Dynamic resource
provisioning
Planned
downtime
• Rolling patch updates
System • Rolling release upgrade
changes using Data Guard
SQL Apply
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Oracle Data Guard and
Real Application Clusters
Oracle Data Guard and Real Application Clusters are
complementary and can be used together.
• Real Application Clusters provides high availability.
• Oracle Data Guard provides disaster protection and
prevents data loss.
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Maximum Availability Architecture
Clients
Oracle WAN traffic Oracle
Application manager Application
Server Server
Data Guard RAC RAC
RAC
production physical logical
database standby standby
database database
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Summary
In this lesson, you should have learned how to:
• Describe the basic components of Oracle Data Guard
• Describe the differences between physical and logical
standby databases
• Determine when Oracle Data Guard is an appropriate
solution in your Oracle Database configuration
• Explain the use of Data Guard in high-availability
architectures
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Practice 1: Overview
This practice covers the following topics:
• Reviewing the factors that affect planned and unplanned
downtime
• Reviewing the differences between physical and logical
standby databases
• Reviewing the components of Oracle Data Guard
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1 - 20 Copyright © 2006, Oracle. All rights reserved.
