distributed databases and ddbms. understand the concept of “distributed data” describe various...
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DISTRIBUTED DATABASES AND DDBMS
Understand the concept of “Distributed Data”
Describe various Distributed Data and DDBMS implementations
Explain how database design affects the DDBMS environment
Apply DDBMS principles to solve problems
Learning Objectives
Distributed Database: A single logical database that is spread physically across computers in multiple locations that are connected by a data communications link
Decentralized Database: A collection of independent databases on non-networked computers
They are not the same thing!
Definitions
What are we talking about here?Key Questions:Are components of the application in
more than one place?Are the data in more than one place?Does the app use more than one DBMS
or “system” for data management?Which facets, if any, are transparent to
users?
Why distribute your app or data? It’s hard. It’s complex. So why do it?
Scalability. Redundancy.
Application Complexity
Monolithic
Everything works / is contained within one computer.
Ex. Ms Word
Distributed
Various working pieces are in different physical places, working over a computer network.
Ex. Google Docs
Data Distribution
Single Site Data (Simple)
All data stored in / retrieved from one place on a network.
Ex. Wordpress
Multi-Site Data (Complex)
Various parts of the data come from various sites on a network.
Ex. My Slice, DNS
Data Complexity
All data associated with the application is stored in the same DBMS
Ex. Wordpress
Various data components of the application are stored in different DBMSes
Ex. SU Blackboard, Facebook
Homogeneous (Easier)Heterogeneous (More Difficult)
Multisite Data DBMS Options Horizontal Partitioning –
Distributing data by row Vertical Partitioning –
Distributing data by table or column. Replication –
Copying data either on a schedule or in real-time
Summary: The taxonomy
App
Monolithic
Distributed
Single Site
Multi Site
Homo.Hetero.
Multi Site
Horiz. Partition
edVert.
Partitoned
Replicated
Homogeneous == Same DBMS
• Customers• Sales Staff
• Orders
CRM Db
• Customers• Sales Staff
N. America
• Orders
Europe
User’s View of Db
Actual Implementation
Oracle OracleSame
Heterogeneous == Multiple DBMS
• Customers• Sales Staff
• Orders
CRM Db
• Customers• Sales Staff
N. America
• Orders
Europe
User’s View of Db
Actual Implementation
Oracle MySQL
• Orders Invoices
Europe
File System
Example of Replication
• Customers• Sales Staff
• Orders
CRM Db
• All Customers• All Sales Staff
• All Orders
N. America
• All Customers• All Sales Staff
• All Orders
Europe
User’s View of Db
Actual Implementation
Master Replica
Example of Horizontal Partitioning
• Customers• Sales Staff
• Orders
CRM Db
• NA Customers• NA Sales Staff
• NA Orders
N. America• E Customers• E Sales Staff
• E Orders
Europe
User’s View of Db
Actual Implementation
Example of Vertical Partitioning
• Financials• Customer Service
• Prod. Support• Human Resources
ERP System
• Financials• Human Resources
N. America• Customer
Service• Prod Support
Europe
User’s View of Db
Actual Implementation
5 Typical Distributed Databases Centralized with Single Site Data Replicated with Snapshots (in real
time) Replicated with Synchronization (on
demand, or a schedule) Integrated Partitions ( Paritioning in
data center) Independent Partitions
(Geographically distributed partitioning)
5 Typical Distributed Databases
Location Transparency User/application does not need to know where data
resides Replication Transparency
User/application does not need to know about duplication of data
Failure Transparency Either all or none of the actions of a transaction are
committed
Transparency is difficult but important. The greater the distribution of data the more there will be a need for transparency to offset the complexity.
Transparency
Applying The Concepts Via Example:
Monolithic or Distributed? Single Site or Multi Site data? If multi-site:
H / V Partitioned or Replicated? Homogeneous or Heterogeneous?
Location Transparency? Replication Transparency? Failure Transparency?
DISTRIBUTED DATABASE AND DDBMS
Questions?