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Oracle Fusion Middleware Architecture Reference for Oracle Unified Directory 11g Release 1 (11.1.1)
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Document Information


1.  Introduction

2.  The Directory Server Access Control Model

3.  Understanding the Directory Server Schema

4.  Directory Server Index Databases

5.  Directory Server Replication

Overview of the Directory Server Replication Architecture

Basic Replication Architecture

Replication Servers

Replication Change Numbers

Replication Server State

Operation Dependencies

How Replication Works

Replication Initialization

Directory Server Change Processing

Replication Server Selection

Replication Server Selection Algorithm

Replication Server Load Balancing

Change Replay

Auto Repair

Directory Server Crashes

Replication Server Crashes

Historical Information and Conflict Resolution

What is a Replication Conflict?

Resolving Modify Conflicts

Resolving Naming Conflicts

Purging Historical Information

Schema Replication

Schema Replication Architecture

Replication Status

Replication Status Definitions

Degraded Status

Full Update Status and Bad Generation ID Status

Replication Groups

Assured Replication

Assured Replication Modes

Safe Data Mode

Safe Read Mode

Safe Read Mode and Replication Groups

Assured Replication Connection Algorithm

Assured Replication and Replication Status

Assured Replication Monitoring

Fractional Replication

Fractional Data Set Identification

Fractional Replication Filtering

Fractional Replication and Local Operations

External Change Log

How the External Change Log Works

Porting Applications That Rely on Other Change Logs

Differences Between the ECL and the LDAP Change Log Draft

Index Differences

DIT and Schema Differences

Additional Differences Between the ECL and the Oracle Directory Server Enterprise Edition Retro Change Log

API for Compatibility With the LDAP Change Log Draft and the Oracle Directory Server Enterprise Edition Retro Change Log

Limitations of the Compability API

6.  Directory Server Root Users and the Privilege Subsystem

7.  Supported Controls and Operations

Schema Replication

This section describe how schema replication is implemented. and is aimed at users who require an in-depth understanding of the schema replication architecture.

Schema describe the entries that can be stored in a directory server. Schema management is a core feature of the directory service. Replication is also a central feature of the directory service and is essential to a scalable, highly available service.

Any changes made to the schema of an individual directory server must therefore be replicated on all the directory servers that contribute to the same service.

Schema replication occurs when the schema is modified in any of the following ways:

Generally, schema modifications occur only when deploying new applications or new types of data. The rate of change for schema is therefore low. For this reason, the schema replication implementation favors simplicity over scalability.

Schema replication is enabled by default. In certain specific cases, it might be necessary to have different schema on different directory servers, even when the servers share all or part of their data. In such cases you can disable schema replication, or specify a restricted list of servers that participate in schema replication. For more information, see Configuring Schema Replication in Oracle Fusion Middleware Administration Guide for Oracle Unified Directory.

Schema Replication Architecture

The schema replication architecture relies on the general replication architecture. You should therefore have an understanding of the general replication architecture before reading this section. For more information, see Overview of the Directory Server Replication Architecture.

Directory servers notify replication servers about any changes to their local schema. As in the case of data replication, the replication servers propagate schema changes to other replication servers, which in turn replay the changes on the other directory servers in the topology.

Schema replication shares the same replication configuration used for any subtree:

dn: cn=example,cn=domains,cn=Multimaster Synchronization,\
  cn=Synchronization Providers,cn=config
objectClass: top
objectClass: ds-cfg-replication-domain
cn: example
ds-cfg-base-dn: cn=schema
ds-cfg-replication-server: <server1>:<port1>
ds-cfg-replication-server: <server2>:<port2>
ds-cfg-server-id: <unique-server-id>

Schema replication differs from data replication in the following ways: