Flat File System 95y2i

UNIT I Overview of Database System

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Overview of Database System • RDBMS • Managing Data 1. Database Design and Application 2. Data Analysis 3. Concurrency and Robustness 4. Efficiency and Scalability

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Difference between Flat File System and DBMS • In traditional file processing 2 (or more) files used to store information. But in DBMS a single repository is shared among multiple s (saves storage space). • Characteristics of DBMS over file system are….

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Difference between Flat File System and DBMS

• Self Describing nature of a Database System – DBMS catalog contains information such as

• Complete definition (description) of the DB structure • Constraints • Structure of each file • The type and storage format of each data item • The DBMS software must work equally well with any number of DB applications as long as the DB definition is stored in the catalog.

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Difference between Flat File System and DBMS

• Insulation between programs and data: – Called program-data independence (w.r.t OODB It is Program operation independence) – Allows changing data structures and storage organization without having to change the DBMS access programs.

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Difference between Flat File System and DBMS

• Data Abstraction: – Hiding implementation details(i.e. high level details) from end . Eg:In case of storage of data in database can only access the database, but implementation details such as how the data is stored physically onto the disc is hidden from . – A data model is used to hide storage details and present the s with a conceptual view of the database.

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Difference between Flat File System and DBMS

• A data model is a collection of concepts for describing data properties and domain knowledge: – Data relationships – Data semantics – Data constraints Eg: Entity-relationship Model • Diagrammatic representation • Easier to work with

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Difference between Flat File System and DBMS

• of multiple views of the data: – Each may see a different view of the database, which describes only the data of interest to that .

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Difference between Flat File System and DBMS

• Sharing of data and multi- transaction processing: – Allowing a set of concurrent s to retrieve from and to update the database. – Concurrency control within the DBMS guarantees that each transaction is correctly executed or aborted – Recovery subsystem ensures each completed transaction has its effect permanently recorded in the database

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Flat File System Disadvantages Advantages Simpler to use Less expensive·

Fits the needs of many small businesses and home s Good for database solutions for hand held devices such as Palm Pilot

Typically does not multi access

Limited to smaller databases(Size) Limited functionality (i.e. no for complicated transactions, recovery, etc.)

1.Redundancy and Integrity issues 2.Use should write separate program to perform each task(it may be complex) 3. No security 4. No backup & recovery 5. No Protection for data in 10 concurrent access

Advantages Greater flexibility

DATABASE

Good for larger databases

Disadvantages

Greater processing power

Difficult to learn

Fits the needs of many medium to large-sized organizations

Requires skilled s

Storage for all relevant data

Expensive

Ensures data integrity between transactions (ACID = atomicity, consistency, isolation, durability) s simultaneous access Provides backup and recovery controls Advanced security

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Advantages of Using the Database Approach • Controlling redundancy in data storage. – Sharing of data among multiple s. • Restricting unauthorized access to data. • Providing Storage Structures (e.g. indexes) for efficient Query Processing

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Advantages of Using the Database Approach

• Providing backup and recovery services. • Providing multiple interfaces to different classes of s. • Representing complex relationships among data. • Enforcing integrity constraints on the database and security. • Data Independence 13

Advantages of Using the Database Approach

• Efficient data access • Data istration • Concurrent access and recovery

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Other Advantages of Using the Database Approach

• Flexibility to change data structures: – Database structure may evolve as new requirements are defined.

• Availability of current information: – Extremely important for on-line transaction systems such as airline, hotel, car reservations.

• Reduced application development Time

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Use a DBMS when this is important • • • • • • • • • •

persistent storage of data centralized control of data control of redundancy control of consistency and integrity multiple sharing of data data documentation data independence control of access and security backup and recovery

Do not use a DBMS when 

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the initial investment in hardware, software, and training is too high the overhead for security, concurrency control, and recovery is too high or not required data and applications are simple and stable real-time requirements cannot be met by it multiple access is not needed Disadvantages of DBMS

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• Edgar Frank "Ted" Codd (August 23, 1923 – April 18, 2003) was a British computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He made other valuable contributions to computer science, but the relational model, a very influential general theory of data management, remains his most mentioned achievement. 18