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Oracle Data Guard
Ensuring Disaster Recovery for Enterprise Data
Enterprise Technology Centre
Introducing Oracle Data Guard
Oracle Data Guard is the most
effective and comprehensive
Disaster Recovery solution
available today for enterprise data
Oracle’s High Availability (HA)
Solution Stack
System
Failure
Unplanned
Downtime
Data Failure
& Disaster
Human Error
System
Maintenance
Planned
Downtime
Data
Maintenance
Real Application Clusters
Continuous Availability for all Applications
Data Guard
Zero Data Loss
Flashback Query
Enable Users to Correct their Mistakes
Dynamic Reconfiguration
Capacity on Demand without Interruption
Online Redefinition
Adapt to Change Online
Oracle Data Guard Focus
 Data Failures & Site Disasters:
–
–
–
Data Protection
Data Availability
Data Recovery
Data is the core asset of
the enterprise!
• Eliminates and reduces downtimes that could occur
because of human errors & planned maintenances
What Is Oracle Data Guard?
 Database software infrastructure that automates the
creation and maintenance of a duplicate, or standby
copy, of the production (or primary) database
 If the primary database becomes unavailable
(disasters, maintenance), the standby database can
be activated and can take over the data serving
needs of the enterprise
How Does It Work?
 As primary database is modified, redo data is
propagated to standby databases
 Standby databases kept synchronized with primary
 Primary database is open and active; standby
database is either in recovery or open read-only /
read-write
 Standby database can be transitioned to the primary
role as necessary
Oracle Data Guard Architecture
Physical Standby
Database
Sync or Async
Redo Shipping
Backup
Production
Database
Redo Apply
DIGITAL DATA STORAGE
DIGITAL DATA STORAGE
Network
Broker
Optional
Delay
Transform
Redo to SQL
Optional
Delay
Logical Standby
Database
SQL
Apply
Open for
Reports
Additional
Indexes & MVs
Data Guard Redo Apply
Data Guard Broker
Physical Standby
Database
Primary
Database
Optional
Delay
Backup
Network
Sync or Async
Redo Shipping
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DIGITAL DATA STORAGE
Redo Apply
Physical Standby Database is a block-for-block copy of the primary database
Uses the database recovery functionality to apply changes
Can be opened in read-only mode for reporting/queries
Can also perform backup, offloading production database
Data Guard SQL Apply
Additional
Indexes &
Materialized Views
Data Guard Broker
Primary
Database
Logical Standby
Database
Optional
Delay
Continuously
Open for Reports
Network
Sync or Async
Redo Shipping

Logical Standby Database is an open, independent, active database

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

Transform Redo
to SQL and Apply
Contains the same logical information (rows) as the production database
Physical organization and structure can be very different
Can be queried for reports while logs are being applied via SQL
Can create additional indexes and materialized views for better query performance
Standby Databases Are Not Idle
Standby
Server
Read-Only / Read-Write
Reporting
Standby
Database
Tape
Backups
Standby database can be used to
offload the primary database, increasing the ROI
Protection from Human Errors
and Data Corruptions
Standby Site
Primary Site
Standby
Database
Production
Database
Optional Delayed
Apply

The application of changes received from the primary can be
delayed at standby to allow for the detection of user errors and
prevent standby to be affected
Switchover and Failover
 Primary and Standby role transitions
 Switchover
–
–
–
Planned role reversal
No database reinstantiation required
Used for maintenance of OS or hardware
 Failover
–
–
Unplanned failure (e.g. disasters) of primary
Primary database must be reinstantiated
 Initiated using simple SQL / GUI interface
Flexible Data Protection Modes
Protection Mode
Risk of Data Loss
Redo Shipment
Maximum Protection
Zero
Synchronous redo
Double Failure Protection shipping to 2 sites
Maximum Availability
Zero
Single Failure Protection
Synchronous redo
shipping
Maximum Performance
Minimal data loss –
usually 0 to few seconds
Asynchronous redo
shipping
Balance cost, availability, performance, and transaction protection
Maximum Protection Mode

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Protection Mode
Risk of Data Loss
Redo Shipment
Maximum Protection
Zero
Double Failure Protection
Synchronous redo
shipping to 2 sites
Highest level of data protection
Enforces protection of every transaction
If last standby is unavailable, processing stops at primary
Good for financial systems where no data loss is acceptable
ALTER DATABASE SET STANDBY TO MAXIMIZE PROTECTION;
Maximum Availability Mode
Protection Mode
Maximum Availability
Risk of Data Loss
Zero
Single Failure Protection
Redo Shipment
Synchronous redo
shipping
 Enforces protection of every transaction
 If last standby is unavailable, processing continues at primary
 When it is re-available, synchronization is automatic
ALTER DATABASE SET STANDBY TO MAXIMIZE AVAILABILITY;
Maximum Performance Mode
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
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
Protection Mode
Risk of Data Loss
Redo Shipment
Maximum Performance
Minimal data loss –
usually 0 to few seconds
Asynchronous redo
shipping
Highest level of performance
Protects from failure of any single component
Least impact on production system
Useful for applications that can tolerate some data loss
ALTER DATABASE SET STANDBY TO MAXIMIZE PERFORMANCE;
Oracle Data Guard Broker
 Distributed management framework that automates
and centralizes the creation, maintenance, and
monitoring of Data Guard configurations
 Management operations can be performed locally or
remotely through the Broker's easy-to-use interfaces:
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GUI-based Oracle Data Guard Manager
Data Guard command-line interface
Data Guard Manager
 Simple, easy-to-use management and monitoring interface
Local and Remote Standby Databases
 Oracle Data Guard configuration can support both local and
remote standby databases
 Local standby database
–
–
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Appropriate for highest data protection modes
LAN links are cheap, reliable, have high bandwidth and low latency
Switchover operations are very fast
 Remote standby database
–
–
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Best solution for disaster recovery
WAN links are generally more expensive, less reliable, have lower
bandwidth and higher latency than LAN links
Suitable for highest performance asynchronous data protection mode
Usage Example
Primary Site
Standby Site A
Standby
Database
Synchronous transport
LAN attached
Used to offload backups
First choice for switchover candidate
Standby Site B
Primary
Database
Synchronous transport
LAN attached
Used to offload reporting
Standby
Database
Asynchronous transport
WAN attached
Delayed apply
Provides DR and data protection
Standby Site C
Standby
Database
Oracle Data Guard and Real
Application Clusters
 Data Guard and Real Application Clusters are complementary and
should be used together
 Real Application Clusters provides high availability
–
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Provides rapid and automatic recovery from node failures or an
instance crash
Provides increased scalability
 Data Guard provides disaster protection and prevents data loss
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By maintaining transactionally consistent copies of primary database
Protects against disasters, data corruption and user errors
Does not require expensive and complex HW/SW mirroring
Data Guard and Remote Mirroring
 Oracle Data Guard’s integrated disaster recovery solution
involving standby databases is often preferred to remote
disk mirroring
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Better network efficiency
Better resilience and data protection
Higher ROI (backup, reporting servers, etc)
 Remote mirroring (ie. HP Continuous Access) can be used
in combination with standby databases to protect nondatabase data