In update-anywhere replication, changes made on any participating database server are replicated to all other participating database servers. This capability allows users to function autonomously even when other systems or networks in the replication system are not available.
Figure 9 illustrates an update-anywhere replication system.
Because each service center can update a copy of the data, conflicts can occur when the data is replicated to the other sites. To resolve update conflicts, Enterprise Replication uses conflict resolution. For more information, see Conflict Resolution.
Review the following information before you select your update-anywhere replication system:
Update-anywhere replication systems allow peer-to-peer updates, and therefore require conflict-resolution (see Conflict Resolution). Update-anywhere replication systems require more administration than primary-target replication systems.
Some risk is associated with delivering consistent information in an update-anywhere replication system. You determine the amount of risk based on the type of conflict-resolution rules and routines you choose for resolving conflicts. You can configure an update-anywhere replication system where no data is ever lost; however, you might find that other factors (for example, performance) outweigh your need for a fail-safe mechanism to deliver consistent information.
All replication systems require you to plan for capacity changes. For more information, see Preparing Data for Replication. In particular, if you choose the time stamp or time stamp plus SPL routine conflict-resolution rule, see Delete Table Disk Space and Shadow Column Disk Space.
If any of your database servers are critical, consider using HDR to provide backup servers. For more information, see High-Availability Replication System.