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

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