If an attribute exists on both the primary and secondary data view, the attribute values are merged by the join data view. For read operations, this implies that a multi-valued attribute is returned, with the values from both data views. For write operations, the proxy queries both data views and determines where to write the value based on the content of the write operation.
If one backend data source fails during an add operation Directory Proxy Server performs an automatic rollback. The roll back takes the form of a delete operation on the data source that did not fail. This ensures the consistency of the data between the two data sources. If a roll back cannot be performed, an error is logged and an optional administrative alert is raised. Automatic roll back is on by default. You can configure automatic roll back by setting the revertAddOnFailure attribute to off (directly in cn=config).
If one backend data source fails during a delete operation, no roll back is performed. An error is logged and an optional administrative alert is raised.