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Database Systems 본문

Database (데이터베이스)

Database Systems

9taetae9 2023. 10. 20. 11:24
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DBMS supports database languages that allow users to express what they want to do with database

QUEL, SQL, relational algebra, query-by-example, LDL, etc.

 

Application programs generally access databases through

-procedural extension of SQL

-embedding SQL in host program languages 

-application program interface (e.g. ODBC/JDBC)

 

DBMS Components

-two key components(query processor, storage manager)

1.query processor : query processing, authorization, authentication etc.

2.storage manager : efficient storing(retrieving and updating of data), file organization(Indexing and hashing), transaction management, etc.

 

simplified database system

user1,2.... n <=> application 1,2,..., n <=> DBMS servers(query processor <->storage manager)<=> DB, meta data(데이터에 관한 구조화된 데이터, 속성 정보라고도함)

 

Data dictionary 

Data dictionary contains metadata(i.e. data about data)

-Data schema(데이터 스키마), Integrity constraints(무결성 제약), Authorization(접근권한), Statistical data

스키마는 DB의 구조와 제약 조건에 관한 전반적인 명세를 정의한 메타데이터의 집합

DBMS references data dictionary to process database languages

 

Transaction Management

-sequence of database operations that performs a single logical function in database applications

-transaction management has two components(concurrency control, recovery manager)

concurrency control manger controls the interation among the concurrent transactions to ensure the consistency of the database

-recovery manager ensures that the database remains in a consistent(correct) state despite of failures

 

Database users(differentiated by the way they expect to interact with the system)

1.naive users 

-invoke one of the permanent application programs that have been wirtten previously 

2.app programmers

3.database designer

4.database analysts 

5.database administrator(DBA)

Database Administrator(DBA)

-coordinates all the activities of the database system

-database administrator's duties(schema def,storage stucture&acces method def, schema&physical organization modification, authorization of users to acces databases, specifying integrity constraints, acting as liaison with users, monitoring system performance etc.)

 

Database System Architecture

-architecture of a database systems is influenced by the underlying computer system on which the database is running

Centralized, Distributed, Client-server,parallel(multi-processor)

 

 

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