Database Management System (DBMS)

DBMS Concepts

What is a Database?
American Heritage Dictionary: a collection of data organized for easy and speed of search and retrieval
Another Perspective
Related to data, perhaps lot of them
#same characteristics
#over long period of time (months, years, …)
Pertinent to people who use the data
Might or might not be of interest to other

Definition and Properties
Definition: A database is a collection of data central to some enterprise that is managed by a Database Management System (DBMS)

Properties:
#Essential to operation of enterprise (contains the only record of enterprise activity)
#Valuable to the enterprise (Historical data can guide enterprise strategy, might be of interest to other enterprises)
#Reflection of the state of the enterprise (database is persistent)

DBMS

is a Specialized software manages databases
#create new databases
#modify existing databases (update data, create reports for different purposes)

Supports
#high-level access language (e.g. SQL)
#application describes database accesses using that language.

Provides users with
#Persistent storage: like file system but much more flexible
#Programming interface: accessing and modifying data through a query language
#Transaction management: concurrent access to data

Overview of a DBMS
#Storage manager: uses OS techniques in memory management (buffer, page, read/write pages)
#Query processor: receive queries, create query plans, send to execution engine, primitive commands (index, file, record requests), which will be satisfied by the corresponding manager .
#Transaction manager: maintains the consistency of the database (control read from/write to a database, concurrency execution, recovery) commands


Features of a DBMS
#DBMS stores a rich set of data types images, audio, geographic data
#DBMS provides online access requests are processed at the time they are initiated
#DBMS allows concurrent access multiple transactions may be processing at the same time

#DBMS may involve distributed data a single transaction may need to access multiple networked sources
#DBMS may involve distributed processing complex operations are not necessarily carried out where the data is stored
# DBMS application may be heterogeneous a single application may span multiple DBMS implementations/systems


People in Design, Implementation, and Maintenance of a Database

#System Analyst - specifies system using input from customer; provides complete description of functionality from customer’s and user’s point of view
#Database Designer - specifies structure of data that will be stored in database
#Application Programmer - implements application programs (transactions) that access data and support enterprise rules
#Database administrator:
o set-up databases
o creates new schema
o modifies existing schema
o manages users (authorization, permission, etc.)
o uses Data Definition Language – a specialized language for creating and defining database schema .
#System Administrator - maintains transaction processing system: monitors interconnection of HW and SW modules, deals with failures and congestion

Nine Functions of a DBMS
1. Update and retrieve data
2. Provide catalog services
3. Support concurrent update
4. Recover data
5. Provide security services
6. Provide data integrity features
7. Support data independence
8. Support data replication
9. Provide utility services