Proxy servers for the directory server

You can configure Tivoli® Directory Server for high availability by setting up proxy servers. The proxy servers contain information about the other servers in an environment and communicate with Tivoli Directory Servers to act as a failover agent.

The proxy directory server provides request routing, load balancing, failover, and distributed authentication. The proxy server also supports distributed or partitioned data, but the proxy server itself holds no data.

Tivoli Directory Server uses peer-to-peer replication to share data across the servers. The peer directory servers are supported and accessed through proxy servers that are configured in the warm standby configuration model. The active proxy server node is accessed through a Service IP address. You can use System Automation for Multiplatforms to achieve high availability for the directory server proxy servers.

The following diagram shows the proxy directory server, which is supported by a standby proxy server.

The diagram is explained in the main body of the text.

To ensure high availability, a second proxy server is available to act as a standby server. When a failure occurs, the proxy server attempts to connect with one or more of the back-end servers. If the proxy server cannot connect to the back-end servers during startup, it starts in configuration-only mode. When the proxy server starts, it queries the replication topology for every back-end server and classifies the back-end servers into two types. The back-end server that is the master of the subtree in the partition is writeable; all remaining back-end servers are readable.

The proxy server locates the first available writeable server and sends all update requests to that server. If the writable server goes offline, the proxy automatically fails over to the next available writeable server. The process repeats if any subsequent servers fail.



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