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Sun OpenDS Standard Edition 2.0 Architectural Reference

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Document Information

The Directory Server Access Control Model

Understanding the Directory Server Schema

Index Databases

Understanding Directory Server Plug-Ins

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

Directory Server Change Processing

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

Replication Server Selection

Replication Groups in a Multi-Data Center Deployment

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

Root Users and the Privilege Subsystem

Supported Controls and Operations

Operation Dependencies

Sometimes an operation cannot be replayed until another operation is complete. For example, when an add operation is followed by a modify operation on the same entry, the server must wait for the add operation to be completed before starting the modify operation.

Such dependencies are quite rare and are generally necessary for a few operations only. Most operations do not have dependencies (since most are modify operations). In such cases, it is necessary to replay operations in parallel to obtain the best performance with multi-CPU servers.

The replication model is built on the assumption that operation dependencies are rare. The replication mechanism therefore always tries to replay operations in parallel, and only switches to processing operation dependencies if an operation fails to replay.