The Worlds of Database Systems From: Ch. 1 of A First Course in Database Systems, by J. D. Pullman and H. Widom

The World of DBS2 Background Business applications of DBs –maintaining internal records, –presenting data to customers and clients on the WWW, and –supporting many other commercial processes Scientific applications, representing data gathered –by astronomers, –by investigators of the human genome, and –by biochemists exploring the medicinal properties of proteins, –etc.

The World of DBS3 Background A database management system (DBMS or a database system) is a powerful tool for creating and managing large amount of data efficiently and allowing it to persist over long period of time, safely. Capabilities of a DBMS –Persistent storage –Programming interface –Transaction management

The World of DBS4 1.1 The Evolution of Database Systems The DBMS is expected to: 1.Allow users to create new data and specify their schema. 2.Give users the ability to query the data 3.Support the storage of very large amount of data 4.Control access to data from many users at once

The World of DBS Early Database Management Systems The first commercial DBMS appears in late 1960 ’ s. –Evolved from file systems Providing (3), storage of large amount of data No direct support of query language Supporting (1), a limited schema for the creation of directory structures of files Not satisfying (4) Applications of the first DBMS –Airline reservation systems –Banking systems –Corporate Records

The World of DBS Relational Database Systems accountNobalancetype saving checking... SELECT balance FROM Accounts WHERE accountNo=67890 SELECT accountNo FROM Accounts WHERE type=‘savings’ AND balance <0

The World of DBS Smaller and Smaller Systems Originally large and expensive Today –many gigabytes fit on a single disk –feasible to run a DBMS on a PC –become available for even very small machines –a common tool for computer applications, much as spreadsheet and word processors did before

The World of DBS Bigger and Bigger Systems Corporate databases often occupy hundreds of gigabytes. –Retails chains often store tetrabytes (10 12 bytes) of information recording the history of every sales made over a long period of time. Multimedia data –An hour of video consumes about a gigabyte. –Databases storing images from satellites can involve petabytes (10 15 bytes) of data. Trends allowing DBSs to deal with large amount of data –Tertiary storage –Parallel computing

The World of DBS Client-Server and Multi-Tier Architectures The simplest client/server architecture –the entire DBMS is a server –the query interfaces that interact with the user and send queries or other commands across to the server A trend to put more works in the client –two tier (client/server) becoming three (or more) tiers –The DBMS continues to acts as a server, but its client is typically an application server, which manages connection to the DBS, transaction, authorization, and other aspects

The World of DBS Multimedia Data Common forms of multimedia data –video, audio, radar signals, satellite images, and documents or pictures in various encoding The storage of multimedia data has forced DBMS ’ s to expand in several ways. –E.g., the operations that one performs on multimedia data are not the simple ones suitable for traditional data forms. –To allow users to create and use complex data operations, DBMS ’ s have to incorporate the ability of users to introduce functions of their own choosing. –The size of multimedia objects also forces the DBMS to modify the storage manager so that objects or tuples of a gigabyte or more can be accommodated.

The World of DBS Information Integration A large company has many divisions. –Each has its own database of products independently of other divisions. –These divisions may use different DBMS ’ s, different structures for information, perhaps even different terms to mean the same thing or the same term to mean different things. Central control is not always the answer. One popular approach is the creation of data warehouses, where information from many legacy databases is copied, with the appropriate translation, to a central database

The World of DBS Overview of a DBMS Data-definition language commands Overview of Query processing Answering the query Transaction processing Storage and buffer management Transaction Processing The query processor

The World of DBS13 Single boxes: system components Double boxes: in-memory data structures Solid lines: control and data flow Dashed lines: data flow only Database management system components

The World of DBS Outline of Database-System Studies Design of databases –Chapters 2, 3 and 4 Database programming –Chapters 5 through 10 Database system implementation –Storage management –Query processing –Transaction management