Chapter 11. Implementing and Understanding Replication Methodologies

O BJECTIVES

The Microsoft-specified objectives for the Replication section of the Database Development SQL Server 2000 exam are as follows :

Alter database objects to support replication

• Support merge, snapshot, and transactional replication models.

• Resolve replication conflicts.

• This objective looks at the different replication model types available. The replication types are merge, transactional, and snapshot; each of these models is covered in detail. This objective also requires that you be able to troubleshoot the different replication processes. To have a thorough understanding of replication, as well as the ability to make appropriate implementations , you need to study replication internals and physical models in more detail than you did in Chapter 3, "Physical Database Design."

O UTLINE

Replication

Benefits of Replication

Understanding Replication Components : The Publisher/Subscriber Metaphor

Publisher

Distributor

Subscriber

Articles and Publications

Horizontal and Vertical Partitions

Subscriptions

Replication Configurations

Central Publisher, Multiple Subscribers

Multiple Publishers, Multiple Subscribers

Multiple Publishers, Single Subscriber

Single Publisher, Remote Distributor

Types of Replication

Transactional Consistency in Replication

Latency in Replication

Snapshot

Transactional Replication

Merge Replication

Replication Agents

The Snapshot Agent

The Log Reader Agent

The Distribution Agent

The Merge Agent

The Queue Reader Agent

Replication Internals

Inside Snapshot Replication

Inside Transactional Replication

Inside Merge Replication

Updating Subscribers

Immediate Updating

Queued Updating

Remote Agent Activation

Heterogeneous Interoperability

Enabling Replication in Your Application

Configuring the Distribution Server

Apply Your Knowledge

Exercises

Review Questions

Exam Questions

Answers to Review Questions

Answers to Exam Questions

S TUDY S TRATEGIES

• Make sure you have a solid understanding of the Publisher/Subscriber Metaphor.

• Go through the Step by Step so you become familiar with how to implement replication. The exam will not require you to know every step, so you should not spend your time memorizing all the different screens of the wizard. The concept of replication and its effect on the database and front-end applications will be the exam focus.

• Make sure you understand how replication works. Understanding the process and components eliminates the need for memorization, which don't provide you with the skills necessary to implement a strategy in the real world.

• There are not any functions, statements, or stored procedures that need to be learned in this chapter pertaining to the exam. In some real-world scenarios, however, you may want to be able to access the processes that will permit you to use replication- related stored procedures to automate a complex configuration.