This document summarizes a seminar presentation on replication in distributed real-time databases. It defines key terms like distributed databases, real-time databases, and data replication. It explains that replication is used to improve availability and performance. The document outlines different replication models including synchronous and asynchronous, discusses strategies for where and when updates are propagated, and lists some common replication protocols. It concludes that replication is important for real-time distributed databases and different protocols offer varying levels of consistency and performance.

1. A Seminaron
Replication in
Distributed Real Time
Database
Presented By
Ashish Upadhyay, CSE,III Yr.

2. CONTENTS
 Introduction
 Distributed Real Time Database
 Replication
 Why do we need it?
 Replication Model
 Replication Strategies
 Replication Protocols
 Advantages

3. INTRODUCTION
• In real-time distributed database
systems, timeliness of results can be as
important as their correctness.
• The objective is to provide a high degree
of concurrency and thus faster average
response time without violating data
consistency

4. Distributed Real Time
Database
• Database is a collection of data items controlled
by Database Management System.
• A Distributed database is a database allocated
to multiple nodes in a distributed system, where
the database is the object of distribution.
• A Real-time database is a database system
which uses real-time processing to handle
workloads whose state is constantly changing.

5. Data Replication
• A strategy in which multiple copies of
some data are stored at multiple
sites.
• A technique by which database can
meet the demand of real time
application.

6. Why do we need it ?
• Availability
• Performance
Middleware
Architecture
Site 1 File X
Site 2 File X
User 1
User 2
User 3Site 3 File X
Site n File X

7. Replication Model
Replication model can be described using five generic phases
• Request (RE): The client submits an operation to one (or
more) replicas.
• Server Coordination (SC): The replica servers coordinate
with each other to synchronise the execution of the
operation
• Execution (EX): The operation is executed on the replica
servers.
• Agreement Coordination (AC): The replica servers agree
on the result of the execution.
• Response (END): The outcome of the operation is
transmitted back to the client.

8. Replication Strategies
• Grey et al have categorized database replication
protocols using two parameters :
 When update propagation takes place?
 Who can perform updates?

9. When update propagation takes
place ?
Synchronous (Eager) Replication
It keeps all replicas exactly synchronized at all nodes
by updating all the replicas as part of one transaction
Write A
Write B
Write C
Commit
Write A
Write A
Write A
Write B
Write B
Write B
Write C
Write C
Write C
Commit
Commit
Commit
Single Node
Transaction
Three Node Eager
Transaction

10. • Asynchronous (Lazy) Replication
Each transaction updates a replica and the
update is propagated to other replicas
Write A
Write B
Write C
Commit
Write A
Write B
Write C
Commit
Write A
Write B
Write C
Commit
Write A
Write B
Write C
Commit
Single Node
Transaction
Three Node Lazy
Transaction

11. Who Can perform updates ?
Group
Any node with a copy of data item can update it, this is
often called update anywhere.
Object Group

12. • Master
Each object has a master node . Only
master can update the primary copy of the
object. All other replicas are read only.
Object
Master
Object Master

13. Replication Protocols
• Eager Primary Key Replication
• Eager Update Everywhere Replication
• Lazy Primary Key
• Lazy Update Everywhere

14. Advantages
• Availability
• Increased parallelism
• Less Data Movement over Network

15. Conclusion
• Replication is need of hour.
• We can achieve replication in real time
distributed database using any of the
discussed protocols.
• Each protocol is differentiated on behalf of
time execution and consistency in
transaction.
• Area of active research.

16. THANK YOU
QUERY?