Data replication

To ensure the availability of all components of your application server environment, you can use data replication to create a backup copy of your application data. Because the primary and backup copies of the data are hosted by physically separated machines, data replication can also ensure disaster recovery.

Data replication relies on iSeries clustering and remote journaling.

• iSeries clustering
  The iSeries clustering provides the basis for communication between two or more iSeries servers. This communication is necessary to back up your data on a physically separate machine. The iSeries cluster framework also defines a list of events that cause a failover to occur. In the iSeries Information Center, see the Clusters topic in Systems management.
  • For V5R2
  • For V5R3

• Remote journaling
  Remote journaling creates a copy of your applcation data to assure hot backup. The two types of remote journaling are synchronous and asynchronous.
  • In synchronous remote journaling, data is written to both the primary and backup databases simultaneously. Synchronous journaling ensures that no entries are lost in the event of a system failure. However, it can negatively impact performance, because it requires the application to wait while data is written to both databases.
  • In asynchronous remote journaling, data is written to the primary database directly from the application. The application then continues to process client requests while data is copied to the backup system. Asynchronous journaling does not impact application performance, but in the event of a failure, the most recent entries may be lost.