오라클 Data replication solutions

s the world’s leading database, Oracle offers a wealth of options to replicate geographically distributed systems.  Each method has its own features and it is the job of the Oracle professional to choose the one that makes sense for their business requirements:
 

• Data Guard – Data Guard standby databases provide standby databases for failover in system that do not have a high downtime cost.  In a data guard failover, the last redo log must be applied (up to 20 minutes to re-open the standby database), and if the last redo cannot be recovered from the crashed instance, the most recent updates may be lost.
   

• Multi-Master Replication – See the excellent book for implementing multi-master replication.  Uses advanced queuing to cross-pollinate many databases with updates.  Has an advantage over Data Guard because the standby database can be used for updates, and a disadvantage that replication is not instantaneous and update collisions may occur.
   

• Oracle Streams – See the comprehensive book on Oracle Streams Technology by Madhu Tumma.  Ready for production use in Oracle 10g, Oracle Streams allows near real-time replication and support for master-to-master replication.  Oracle Streams has no licensing costs (RAC costs extra) and it is less complex to configure than a RAC database.  This disadvantage over RAC is that there is no continuous availability, update collisions may occur, replication is not instant, and application failover is usually done manually. 
   

• Real Application Clusters – The Cadillac of Oracle continuous availability tools, RAC allows for Transparent Application Failover (TAF) and RAC is de-rigueur for systems with a high cost of downtime and continuous availability on RAC. 

  
  

  원문 : http://www.dba-oracle.com/oracle_tips_multi_master_replication_streams.htm