oracle data guard ensuring disaster recovery for enterprise data enterprise technology centre
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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
Data Failure& Disaster
Human Error
Real Application ClustersContinuous Availability for all Applications
Data GuardZero Data Loss
Flashback QueryEnable Users to Correct their Mistakes
SystemMaintenance
Data Maintenance
Dynamic ReconfigurationCapacity on Demand without Interruption
Online RedefinitionAdapt to Change Online
UnplannedDowntime
PlannedDowntime
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!
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
NetworkBroker
ProductionDatabase
Logical StandbyDatabase Open for
Reports
SQLApplyOptional
Delay
Transform Redo to SQL
AdditionalIndexes & MVs
Physical StandbyDatabase
Optional Delay
DIGITAL DATA STORAGE
DIGITAL DATA STORAGE
Backup
Redo Apply
Sync or Async Redo Shipping
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
OptionalDelay
Sync or Async Redo Shipping
Network
Redo Apply
DIGITAL DATA STORAGE
Backup
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 Async Redo Shipping
NetworkContinuously
Open for Reports
Transform Redo to SQL and Apply
Data Guard BrokerPrimary
Database Logical StandbyDatabase
Standby Databases Are Not Idle
Standby database can be used to offload the primary database, increasing the ROI
Standby Server
StandbyDatabase
Read-Only / Read-Write
Reporting
BackupsTape
Protection from Human Errors and Data Corruptions
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
Primary Site
StandbyDatabase
Standby Site
ProductionDatabase
Optional Delayed Apply
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 ZeroDouble Failure Protection
Synchronous redo shipping to 2 sites
Maximum Availability ZeroSingle 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
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
Protection Mode Risk of Data Loss Redo Shipment
Maximum Protection ZeroDouble Failure Protection
Synchronous redo shipping to 2 sites
ALTER DATABASE SET STANDBY TO MAXIMIZE PROTECTION;
Maximum Availability Mode
Enforces protection of every transaction If last standby is unavailable, processing continues at primary When it is re-available, synchronization is automatic
Protection Mode Risk of Data Loss Redo Shipment
Maximum Availability ZeroSingle Failure Protection
Synchronous redo shipping
ALTER DATABASE SET STANDBY TO MAXIMIZE AVAILABILITY;
Maximum 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
Protection Mode 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;
Local and Remote Standby Databases
Oracle Data Guard configuration can support both local and remote 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 lower
bandwidth and higher latency than LAN links– Suitable for highest performance asynchronous data protection mode
Usage Example
PrimaryDatabase
Primary Site
StandbyDatabase
Standby Site A Synchronous transportLAN attachedUsed to offload backupsFirst choice for switchover candidate
StandbyDatabase
Standby Site B
Synchronous transportLAN attachedUsed to offload reporting
StandbyDatabase
Standby Site C
Asynchronous transportWAN attachedDelayed applyProvides DR and data protection
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– Provides rapid and automatic recovery from node failures or an
instance 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
Data Guard and Remote Mirroring
Oracle Data Guard’s 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