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 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

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

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

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

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

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

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

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

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

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 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

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;

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;

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;

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 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

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

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