3.3.7. Advanced Feature: Configuring Cascading Chaining

The database link can be configured to point to another database link, creating a cascading chaining operation. A cascading chain occurs any time more than one hop is required to access all of the data in a directory tree.

3.3.7.1. Overview of Cascading Chaining

Cascading chaining occurs when more than one hop is required for the directory to process a client application's request. For example:
The client application sends a modify request to Server 1. Server one contains a database link that forwards the operation to Server 2, which contains another database link. The database link on Server 2 forwards the operations to server three, which contains the data the clients wants to modify in a database. Two hops are required to access the piece of data the client want to modify.
During a normal operation request, a client binds to the server, and then any ACIs applying to that client are evaluated. With cascading chaining, the client bind request is evaluated on Server 1, but the ACIs applying to the client are evaluated only after the request has been chained to the destination server, in the above example Server 2.
Consider the following example scenario. On Server A, a directory tree is split as follows:
The root suffix dc=example,dc=comand the ou=people and ou=groups sub suffixes are stored on Server A. The l=europe,dc=example,dc=com and ou=groups suffixes are stored in on Server B, and the ou=people branch of the l=europe,dc=example,dc=com suffix is stored on Server C.
With cascading configured on servers A, B, and C, a client request targeted at the ou=people,l=europe,dc=example,dc=com entry would be routed by the directory as follows:
First, the client binds to Server A and chains to Server B using Database Link 1. Then Server B chains to the target database on Server C using Database Link 2 to access the data in the ou=people,l=europe,dc=example,dc=com branch. Because at least two hops are required for the directory to service the client request, this is considered a cascading chain.