One important requirement for WebSphere Portal is ability to deploy an architecture in geographically distributed fashion.
Geogrphically distributed architecture makes sense either because of the disaster recovery requirement which means that even if one data center is down the application still works. Or when major geography maintains the local services and back-end systems that are effectively accessed through the portal.
With the introduction of database domains in WebSphere Portal Server V6.0.x, greater
flexibility was made possible in terms of the permissible operational architecture. As such, the distinction between release, community, and user customization data has made it possible to achieve a truly "global deployment". Readers familiar with previous versions of WebSphere Portal Server will recall that it was not possible to split the Portal database between multiple redundant clusters, located potentially in different geographies, and to maintain a consistent user experience. Indeed, such an architecture when deployed sacrificed the ability for a user to make any customization or personalization modifications, as the changes simply could not be propagated between clusters. This in part was attributed to the fact that the internal object
IDs associated with the various elements of a deployment could not be guaranteed to be
unique. Any attempt, therefore, to deploy a bi-directional database replication technique was further hindered. To overcome this constraint, it was mandatory that all Portal cluster members, participating in the same Portal instance, accessed the same centralized database. However, the performance considerations of accessing a centralized database across the WAN from geographically dispersed Portal servers made this approach impractical in many environments.
In addition to the separation of Portal data into distinct database domains with WebSphere Portal Server V6.0.x, which represents an acknowledged product improvement, it should also be recognized that Portal data can now be shared between different Portal clusters and the very cluster members that exist within them. Such database domains can now be deployed in a peer-to-peer manner using techniques like queue replication or 2-way SQL replication in order to provide a global deployment capability, where user personalization is automatically made available to all Portal clusters in all geographies. In this manner, WebSphere Portal Server V6.0.x also allows users to experience portability should they temporarily access the Portal solution from another geo (branch or office location).
Important: The implementation of a multi-clustered WebSphere Portal Server V6.0.x
architecture that sees the deployment of individual clusters in each geography to support a truly "global deployment" mandates the use of the same LDAP directory server in all geographies. The LDAP directory server may, however, be replicated for redundancy purposes. This requirement is necessary to maintain uniqueness between Portal users.