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Oracle Data GuardEnsuring Disaster Recovery for Enterprise Data
Enterprise Technology Centre
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Introducing Oracle Data Guard
Oracle Data Guard is the most
effective and comprehensive
Disaster Recovery solutionavailable today for enterprise data
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Oracles High Availability (HA)Solution Stack
System
Failure
Data Failure
& Disaster
Human Error
Real Application ClustersContinuous Availability for all Applications
Data GuardZero Data Loss
Flashback QueryEnable Users to Correct their Mistakes
System
Maintenance
Data
Maintenance
Dynamic ReconfigurationCapacity on Demand without Interruption
Online RedefinitionAdapt to Change Online
Unplanned
Downtime
Planned
Downtime
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Oracle Data Guard Focus
Data Failures & Site Disasters:
Eliminates and reduces downtimes that could occur
because of human errors & planned maintenances
Data Protection
Data Availability Data Recovery
Data is the core asset of
the enterprise!
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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
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How Does It Work?
As primary database is modified, redo data ispropagated to standby databases
Standby databases kept synchronized with primary
Primary database is open and active; standbydatabase is either in recovery or open read-only /read-write
Standby database can be transitioned to the primaryrole as necessary
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Data Guard Configuration
Managed as a single configuration
Primary and standby databases can be single-instance Oracle or
Real Application Clusters
Up to nine standby databases supported in a single configuration
Primary
Database
Standby
Database
StandbySite A
Standby
Database
StandbySite B
PrimarySite
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Oracle Data Guard Architecture
NetworkBroker
ProductionDatabase
LogicalStandbyDatabase Open for
Reports
SQLApply
OptionalDelay
TransformRedo to SQL
AdditionalIndexes & MVs
PhysicalStandbyDatabase
OptionalOptionalDelayDelay
DI
ITALDATA STORA
DI
ITALDATA STORA
Backup
Redo Apply
Sync or AsyncRedo Shipping
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Data Guard 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 Broker
PrimaryDatabase
Physical StandbyDatabase
Optional
Delay
Sync or AsyncRedo Shipping
Network
Redo Apply
DIGITA
DATA STORAG
Backup
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Data Guard SQL Apply
Logical Standby Database is an open, independent, active database
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
Optional
Delay
AdditionalIndexes &
Materialized Views
Sync or AsyncRedo Shipping
Network
ContinuouslyOpen for Reports
Transform Redoto SQL and Apply
Data Guard BrokerPrimary
Database Logical StandbyDatabase
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Standby Databases Are Not Idle
Standby database can be used to
offload the primary database, increasing the ROI
Standby
Server
Standby
Database
Read-Only / Read-Write
Reporting
BackupsTape
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Cascading Standby Database
Standby database that receives its redo data from another
standby database and not from the original primary database
Primary database sends a set of redo data to only selectedstandby databases and not to all standby databases
Reduces the load on the primary system, and also reduces
network traffic and use of valuable network resources around theprimary site
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Protection from Human Errorsand Data Corruptions
The application of changes received from the primary can be
delayed at standby to allow for the detection of user errors andprevent standby to be affected
Primary Site
Standby
Database
Standby Site
ProductionDatabase
Optional Delayed
Apply
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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
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Flexible Data Protection Modes
ProtectionMode Risk of Data Loss Redo Shipment
Maximum Protection Zero
Double Failure Protection
Synchronous redo
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
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Maximum Protection ModeMaximum Protection Mode
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
ProtectionMode Risk of Data Loss Redo Shipment
Maximum Protection Zero
Double Failure Protection
Synchronous redo
shipping to 2 sites
ALTER DATABASE SET STANDBY TO MAXIMIZE PROTECTION;
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Maximum Availability ModeMaximum Availability Mode
Enforces protection of every transaction
If last standby is unavailable, processing continues at primary
When it is re-available, synchronization is automatic
ProtectionMode Risk of Data Loss Redo Shipment
Maximum Availability Zero
Single Failure Protection
Synchronous redo
shipping
ALTER DATABASE SET STANDBY TO MAXIMIZE AVAILABILITY;
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Maximum Performance ModeMaximum Performance Mode
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
ProtectionMode Risk of Data Loss Redo Shipment
Maximum Performance Minimal data loss
usually 0 to few seconds
Asynchronous redo
shipping
ALTER DATABASE SET STANDBY TO MAXIMIZE PERFORMANCE;
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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:
GUI-based Oracle Data Guard Manager
Data Guard command-line interface
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Data Guard Manager
Simple, easy-to-use management and monitoring interface
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Local and Remote Standby Databases
Oracle Data Guard configuration can support both local andremote standby databases
Local standby database 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 Best solution for disaster recovery
WAN links are generally more expensive, less reliable, have lowerbandwidth and higher latency than LAN links
Suitable for highest performance asynchronous data protection mode
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Usage Example
Primary
Database
PrimaryS
ite
Standby
Database
StandbySite A Synchronous transport
LAN attachedUsed to offload backups
First choice for switchover candidate
Standby
Database
StandbySite B
Synchronous transport
LAN attachedUsed to offload reporting
Standby
Database
StandbySite C
Asynchronous transport
WAN attached
Delayed apply
Provides DR and data protection
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Oracle Data Guard and RealApplication Clusters
Data Guard and Real Application Clusters are complementary and
should be used together
Real Application Clusters provides high availability
Provides rapid and automatic recovery from node failures or aninstance crash
Provides increased scalability
Data Guard provides disaster protection and prevents data loss
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
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Data Guard and Remote Mirroring
Oracle Data Guards integrated disaster recovery solution
involving standby databases is often preferred to remote
disk mirroring
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 non-database data
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Why Oracle Data Guard?
1. Disaster Recovery & High Availability Easy failover/switchover between primary and standby databases
2. Complete data protection Guaranteed zero data loss, safeguard against data corruptions
3. Efficient utilization of system resources Standby databases can be used for reporting, backups, queries
4. Balance data availability against performance Flexible data protection/synchronization modes
6. Centralized and simple management Push-button graphical interface for management and monitoring
5. Automatic resynchronization after restoration of network connectivity Automatic archive gap detection and resolution with no manual intervention
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