Monday, February 17, 2014

Oracle Active Data Guard Or Oracle GoldenGate

Oracle Active Data Guard and Oracle GoldenGate

Oracle Active Data Guard and Oracle Golden Gate are strategic capabilities within Oracle's software portfolio. While they generally fall into the category of replication technologies, each has a very different area of focus.
Oracle Active Data Guard provides the best data protection and availability for Oracle Database in the simplest most economical manner by maintaining an exact physical replica of the production copy at a remote location that is open read-only while replication is active. Active Data Guard eliminates compromise inherent in storage remote-mirroring or logical replication solutions though deep integration with Oracle Database and through the simplicity achieved by complete focus on providing real-time data protection and availability for Oracle data.
GoldenGate is an advanced logical replication product that supports multi-master replication, hub and spoke deployment and data transformation, providing customers very flexible options to address the complete range of replication requirements. GoldenGate also supports replication between a broad range of heterogeneous hardware platforms and database management systems. Unlike Active Data Guard, GoldenGate captures primary database changes by reading redo records from disk, transforming those records into a platform independent trail file format, and transmitting the trail file to the target database. GoldenGate maintains a logical replica by converting the trail file into SQL and applying SQL to the target database. The target database is open read-write while synchronization occurs.
When do I use Oracle Active Data Guard?

Use Active Data Guard where emphasis is on simplicity, best data protection, data availability and highest performance:
  • Secure physical replication, standby database is open read-only, it is impossible to modify standby data independent of primary transactions
  • Simplest, fastest, one-way replication of a complete Oracle Database. No requirements for supplemental logging or performance implications for tables having no primary key or unique index. Little if any performance tuning required at the standby database, the default configuration handles most workloads.
  • No restrictions - Oracle Data Guard Redo Apply supports all Oracle features and transparently replicates all data and storage types, PL/SQL packages and DDL without special considerations
  • Best data protection – Replication direct from memory isolates the standby from I/O corruption that can occur at the primary database. Detect silent lost-write corruption that can occur independently on primary or standby. Automatically detect and repair physical block corruption that can occur independently on primary or standby.
  • Choice of synchronous with zero data loss, or asynchronous with near-zero data loss protection
  • Simple to improve ROI by offloading read-only workload and/or backups to a synchronized physical standby
  • Transparency of backups - an Oracle Data Guard primary and standby are physically exact copies of each other, RMAN backups are completely interchangeable
  • Minimize planned downtime and risk using Data Guard standby; standby first patching, database rolling upgrades, and select platform migrations (see My Oracle Support Note 413484.1 for mixed platform combinations)
  • A single command will convert a physical standby database as a test system open read-write. A second command will convert it back to a physical standby database and resynchronize it with the primary; primary data is protected at all times.
  • Integrated management of a complete configuration - Oracle Data Guard Broker command line or Oracle Enterprise Manager Cloud Control, integrated automatic database and client failover
Active Data Guard is a superset of Data Guard capabilities included with Oracle Enterprise Edition and can be purchased as the Active Data Guard Option for Oracle Database Enterprise Edition. It is also included with every Oracle GoldenGate license, offering customers the ability to acquire the complete set of advanced Oracle replication capabilities with a single purchase. Basic Data Guard functionality does not require a separate license, it is included with Oracle Enterprise Edition.

When do I use Oracle GoldenGate?

Use Oracle GoldenGate when a replica database must be open read-write while replication is active, or for advanced replication requirements beyond what is addressed by Active Data Guard:
  • Any requirement where the replica database must be open read-write while synchronizing with the primary database
  • Any advanced replication requirements such as: multimaster and bidirectional replication, subset replication, many to one replication, cross endian replication, and data transformations
  • Maintenance and migrations where zero downtime using bi-directional replication is required
  • Application upgrades that modify back-end database objects. GoldenGate maintains availability and reduces planned downtime by replicating between old and new versions of the database (the user implements mapping between differences in database objects in old and new versions of the database
  • Any cross platform migration not supported by Data Guard (e.g. cross endian platform migration)
  • Any replication requirement where you replicate from a more recent version of Oracle Database to an earlier version of Oracle Database (e.g. from Oracle Database 11g to Oracle Database 10g)

When do I use Active Data Guard and GoldenGate Together

Active Data Guard and GoldenGate are not mutually exclusive. The following examples of high availability architectures that include the simultaneous use of both technologies:
  • An Active Data Guard standby is utilized for disaster protection and database rolling upgrades for a mission critical OLTP database. GoldenGate is used to extract data from the Data Guard primary database (or from the standby database using GoldenGate ALO mode) for ETL update of an enterprise data warehouse.
  • GoldenGate subset replication is used extract, transforms, and aggregate data from numerous data sources into a central operational data store (ODS). The ODS supports mission critical application systems that generate significant revenue for the company. An Active Data Guard standby database is used to protect the ODS, providing optimal data protection and availability.
  • GoldenGate multi-master replication is utilized to synchronize several databases, each located in different geographies. Each GoldenGate copy has its own local synchronous Data Guard standby database that enables zero data loss failover should an outage occur. GoldenGate capture and apply processes are easily restarted on the new primary database following a failover since primary and standby are an exact, up-to-date replica of each other.
  • Reducing planned downtime for various planned maintenance activities not supported by Data Guard – such as cross-endian platform migration or application upgrades that modify back-end database objects. In many cases customers wish to isolate a current mission critical production environment having a Data Guard primary and standby database from being impacted by the maintenance activity. A parallel environment (new primary and standby) is deployed on the new release or new platform and GoldenGate one-way or bi-directional replication is used to keep old and new environments synchronized. Production is moved to the new environment once sufficiently tested. GoldenGate can continue to replicate to the previous environment for fast fall-back until the stability of the new version is no longer in question, at which time the old environment can be de-commissioned.

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