Advanced Replication Setup for High availability and Performance

Posted by Vijayakumar Chinnasamy
October 24th, 2011

In my personal opinion, Oracle leads the market in Directory Product offerings (LDAP Directories). Starting from Oracle Internet Directory (OID), to the latest Oracle Unified Directory (OUD), Oracle definitely provides variety of LDAP Directory related products for integration.

With increasing demand for mobile computing and cloud computing offering, there is a need to standardize LDAP Deployments for Identification, Authentication and (sometimes) Authorization (IAA) services. With a highly scalable, highly performing, highly available, highly stable and highly secure LDAP Directory, these IAA services will be easier to integrate with applications in the cloud or for the mobile applications.


Oracle Unified Directory (OUD) is a latest LDAP Directory offering from Oracle Corp. As mentioned in my previous post, OUD comes with three main components. They are:

  • Directory Server
  • Proxy Server
  • Replication Server

Here, Directory Server provides the main LDAP functionality (I assume you already know what an LDAP Directory Server means). Proxy server is used for to proxy LDAP requests (how?). And Replication Server is used for replicating (copying) data from one OUD to another OUD or even to ODSEE server (we will talk more about replication in this post). You can read about my first post on OUD here. In this current article, I will write about replication server and advanced replication setup for Oracle Unified Directory.

Many people want a step by step guide (kind of cheat sheet) to setup something like OUD or OID for replication. Unfortunately I am not going to give you that here. In my personal opinion, that (cheat sheet) is not a right approach at all and will not be helpful in the long run for gaining concepts or knowledge. First of all, we need to give importance to the basic concepts behind how something works.

First of all, read OUD Documentation

Product Documentation must be read before you plan your deployment. You can find the OUD Documentation here. This link is for OUD Version 11.1.1. Make sure to refer the latest product manual. Documentation provides lot of details about the product and save lot of time with investigation later. For Replication, you need to start with “Architecture Reference” Guide.

When do you want to setup replication?

There should be a reason, right? If there is no reason, then there is no need for you to setup replication at all. Instead, you can have a beer and pass the time happily doing something else.

Ideally, you need replication setup for “High Availability” and “Performance”. Usually, there will be multiple instances of OUD Directory Server processes running in Production. Let’s say we need to have around four OUD Directory Servers (and four more for Business Continuity/Disaster Recovery).

Unfortunately, there is no single process to update all the eight OUD Directory Servers in our example. We need to find a mechanism to synchronize the directory entries across these servers.  For this, we need to use the OUD Replication Server Component.

Securing the Replication Traffic

We don’t want network sniffers taking away critical user information (even inside the internal network, it is possible). We need to encrypt the traffic between the replication servers. Do not consider setting up a Replication Server communication without encrypted traffic.

Since OUD provided identity data, all the network traffic is prone to sniffing attacks. Always use encrypted or secure connections to OUD or to any LDAP Directory.

Deciding a Replication Method to use

Next important thing is to decide what replication method you are going to use. This is mostly site specific and you need to know lot of details before deciding a replication method to use. I am planning to use the following sample architecture for this post. Let’s understand our sample OUD Architecture first.

Here are the quick components of the architecture:

  • We have one master OUD Server called PROD-01. All the updates to the directory happens here. Most probably, HR System will update the directory. Also, Updates can happen using a custom developed application plug-in for LDAP Directory or using a Identity and Access Management System (IAM) system such as Oracle Identity Manager or Tivoli Identity Manager.
  • PROD-02 will be used with PROD-01 for High Availability and Performance in this Production Deployment.
  • In Disaster Recovery deployment, we have PROD-03 and PROD-04 servers. These servers need to synchronize the user data from the master server PROD-01.

One way to setup replication is by provisioning users into all the six OUD Directory Servers by an Identity and Access Management (IAM) System (such as Oracle Identity Manager or Tivoli Identity Manager). However this provisioning can be time consuming to complete because it will be treated as updating six different LDAP Directories. So a better way to achieve this is using a Replication Server.

We will continue setting up the Replication Server for this architecture. Lets meet in another post – Until then.

Vijay Chinnasamy

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