1. Oracle Data Guard Ensuring Disaster Recovery for Enterprise Data
Enterprise Technology Centre

2. Introducing Oracle Data Guard
Oracle Data Guard is the most effective and comprehensive Disaster Recovery solution available today for enterprise data

3. Oracle’s High Availability (HA) Solution Stack
System Failure
Real Application Clusters Continuous Availability for all Applications
Data Guard Zero Data Loss
Unplanned Downtime
Data Failure & Disaster
Flashback Query Enable Users to Correct their Mistakes
Human Error
System Maintenance
Dynamic Reconfiguration Capacity on Demand without Interruption
Planned Downtime
Data Maintenance
Online Redefinition Adapt to Change Online

4. 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

5. 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

6. 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

7. Data Guard Configuration
Standby
Database
Standby Site A
Primary Site
Primary
Database
Standby
Database
Standby Site B
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

8. Oracle Data Guard Architecture
Physical Standby
Database
Sync or Async
Redo Shipping
Backup
Production
Database
Redo Apply
Network
Broker
Optional
Delay
Logical Standby
Database
Open for
Reports
SQL Apply
Optional
Delay
Transform
Redo to SQL
Additional
Indexes & MVs

9. Data Guard Redo Apply
Data Guard Broker
Physical Standby
Database
Primary
Database
Optional
Delay
Backup
Network
Redo Apply
Sync or Async
Redo Shipping
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

10. Continuously Open for Reports
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
Transform Redo
to SQL and 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

11. Standby Databases Are Not Idle
Server
Read-Only / Read-Write
Reporting
Standby
Database
Backups
Tape
Standby database can be used to
offload the primary database, increasing the ROI

12. 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 selected standby 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 the primary site

13. Protection from Human Errors and Data Corruptions
Primary Site
Standby
Database
Standby Site
Production
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

14. 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

15. Flexible Data Protection Modes
Risk of Data Loss
Redo Shipment
Maximum Protection
Zero
Double Failure Protection
Synchronous redo shipping to 2 sites
Maximum Availability
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

16. Maximum 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;

17. Maximum Availability Mode
Protection Mode
Risk of Data Loss
Redo Shipment
Maximum Availability
Zero
Single Failure Protection
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;

18. Maximum Performance Mode
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;

19. 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

20. Usage Example Standby Site A Primary Site Standby Site B
Database
Standby Site A
Synchronous transport
LAN attached
Used to offload backups
First choice for switchover candidate
Primary
Database
Primary Site
Standby
Database
Standby Site B
Synchronous transport
LAN attached
Used to offload reporting
Standby
Database
Standby Site C
Asynchronous transport
WAN attached
Delayed apply
Provides DR and data protection

21. 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

22. 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

23. Why Oracle Data Guard? Disaster Recovery & High Availability
Easy failover/switchover between primary and standby databases
Complete data protection
Guaranteed zero data loss, safeguard against data corruptions
Efficient utilization of system resources
Standby databases can be used for reporting, backups, queries
Balance data availability against performance
Flexible data protection/synchronization modes
Automatic resynchronization after restoration of network connectivity
Automatic archive gap detection and resolution with no manual intervention
Centralized and simple management
Push-button graphical interface for management and monitoring