1. Introduction to Replication
Tom Davis
Software Architects, Inc.

2. Overview Introduction to Distributed Data Introduction to Replication
Replication Agents
Replication Types
Physical Replication Models

3. Introduction to Distributed Data
The Need for Distributed Data
Considerations for Distributing Data
Methods to Distribute Data

4. The Need for Distributed Data
Brings Data Closer Together
Allows Site Independence
Separates
OLTP
Read Intensive Applications
Can Reduce Conflicts

5. Distributed Data Considerations

6. Methods to Distribute Data

7. Introduction to Replication
The Publisher-Subscriber Metaphor
Publications and Articles
Filtering Data
Subscriptions

8. The Publisher-Subscriber Metaphor

9. Publications and Articles
The basis of a subscription
A collection of one or more articles
Can have one or more publications per database
Article
Data from a whole or filtered partition of a table or a database object
Part of a publication

10. Filtering Data

11. Subscriptions

12. Replication Agents Snapshot Agent Distribution Agent Log Reader Agent
Prepares initial snapshots and stores them on the distributor
Distribution Agent
Moves snapshot and transactional data to Subscribers
Log Reader Agent
Copies data from transaction log to the distribution database
Merge Agent
Merges changes from multiple sites
Queue Reader Agent
Applies changes from a queue and applies them to multiple subscribers
Cleanup Agents
Complete scheduled and on-demand maintenance of replication

13. Replication Types Overview of the Replication Types
Considerations for Using Merge Replication

14. Overview of the Replication Types
Snapshot Replication
Periodic bulk transfer of new snapshots of data
Transactional Replication
Replication of incremental changes
Merge Replication
Autonomous changes to replicated data are later merged

15. Considerations for Using Merge Replication
Changes to the Schema
Identifies a unique column
Adds several system tables
Creates triggers at Publisher and Subscriber
Conflict resolution
Tracks updates
Compares values and resolves conflicts
Replicates only synchronized data

16. Physical Replication Models
Overview of the Physical Replication Models
Combining Physical Replication Models and Types
Central Publisher/Remote Distributor Example
Central Subscriber/Multiple Publishers Example
Multiple Publishers/Multiple Subscribers Example

17. Overview of the Physical Replication Models

18. Combining Physical Replication Models and Types
The Model is the Physical Implementation
The Type Provides the Functionality
Any of the Models Can Use Any of the Types

19. Central Publisher/Remote Distributor Example

20. Central Subscriber/Multiple Publishers Example

21. Multiple Publishers/Multiple Subscribers Example

22. Recommended Practices
Determine the Acceptable Degree of Data Latency
Select an Appropriate Replication Type
Select the Physical Replication Model
Determine Whether to Allow Updates to Replicated Data