02 Distributed DBMSTechnology
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IT Database Management System 1
Transcript of 02 Distributed DBMSTechnology
A distributed database is a database that is under the control of a central database management system (DBMS) in which storage devices are not all attached to a common CPU
Collections of data (e.g. in a database) can be distributed across multiple physical locations.
To ensure that the distributive databases are up to date and current, there are two processes: replication and duplication
Besides distributed database replication and fragmentation, there are many other distributed database design technologies.
A distributed database management system ('DDBMS') is a software system that permits the management of a distributed database and makes the distribution transparent to the users.
Sometimes "distributed database system" is used to refer jointly to the distributed database and the distributed DBMS.
Figure 2.1 – Example of Distributed Database System.
A database Users access the distributed database through:
1. Local Applications
2. Global Applications
A distributed database does not share main memory or disks.
ACID (Atomicity, Consistency, Isolation, and Durability) is a set of properties that guarantee that database transactions are processed reliably.
A-atomicity: the transaction takes place as whole or not at all.
C-consistency: maps one consistent DB state to another
I-isolation: each transaction sees a consistent DB.
D-durability: the results of a transaction must survive system failures
1. Reflects organizational structure 2. Local autonomy
3. Protection of valuable data
4. Improved performance
5. Economics
6. Modularity
7. Reliable transactions
1. Complexity 2. Economics
3. Security
4. Difficult to maintain integrity
5. Inexperience
6. Lack of standards
7. Database design more complex 8. Additional software is required
9.Operating System should support distributed environment
10. Concurrency control
