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MSc IT UFCE8K-15-M Data Management Prakash Chatterjee Room 2Q18

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Presentation on theme: "MSc IT UFCE8K-15-M Data Management Prakash Chatterjee Room 2Q18"— Presentation transcript:

1 MSc IT UFCE8K-15-M Data Management Prakash Chatterjee Room 2Q18 Lecture 9 : DBMS Architecture

2 UFCE8K-15-M Data Management 2013/142 ANSI/SPARC Architecture o Problem of Data independence o In ‘classical systems’ o Application programs ‘know’ about how and where data is stored o Problems when additional data stored but not of relevance to prog data reorganised for efficiency but no change in content

3 UFCE8K-15-M Data Management 2013/143 ANSI/SPARC (2) o Two distinctions o between the global ‘logical’ data model and the way the data is stored in physical data storage on disk o isolates issues of efficient storage such as indexes, replication of data for fast access and backup o between local application programs and the global data model o isolates functional areas from concern for the full conceptual model - remember ISIS has 250 tables

4 UFCE8K-15-M Data Management 2013/144 ANSI/SPARC (3) o External view - defines VIEWS which bring together a subset of the full model for a specific functional area - e.g. enrolment o Conceptual model - full ‘logical’ model of the organisation o Physical - storage of data in underlying files using the appropriate file structures, and allocated to storage units

5 UFCE8K-15-M Data Management 2013/145 ANSI/SPARC example o Lecturer view of ISIS o those students which she teaches (restriction) o relevant data items (projection) o denormalised (eg. name and award name by module) o Full model is 250 tables o Physical data storage o duplicates key files for fast retrieval o builds indexes based on common queries

6 UFCE8K-15-M Data Management 2013/146 DBMS Software Components o User programs o user developed programs (eg. as VB Macros, PLSQL procedures, PHP scripts,stored Queries) o DBMS Toolkit o tools to help user build systems and user programs o Interface o language and protocol for communication between User programs and Kernel o Kernel o core Database functions - data storage and retrieval o Operating System - file storage

7 UFCE8K-15-M Data Management 2013/147 Interface o User programs need to communicate with the Kernel to o update the Schema (Data Definition Language) o update the Factbase (Data Manipulation Language) o Interface must handle: o sending requests to the Kernel e.g. with SQL o receiving results from the Kernel o linking to Kernel, handling errors (e.g ODBC,JDBC) o Receiving results is tricky: o send whole relation in some serialized format o send pointer to temporary table and get each row

8 UFCE8K-15-M Data Management 2013/148 Interface (2) o Scripting languages such as PL/SQL (Oracle’s application language) and PHP (a Web server language) send SQL and provide routines for access to the results e.g. o the notion of a ‘CURSOR’ a pointer to the next row of a table to be returned o Access can automate this connection so that a table located on a remote server ‘appears’ to be a local table.

9 UFCE8K-15-M Data Management 2013/149 Kernel functions o CRUD - Create, Read, Update, Destroy o at Factbase and Schema level o Data Dictionary - Schema storage o Transaction Management - run-unit completion o Concurrency Control - multiple users o Recovery - backup and restore o Authorisation - users, passwords, areas o Data Communications ( or by OS) o Data integrity - foreign keys etc. o Import/Export, Monitoring

10 UFCE8K-15-M Data Management 2013/1410 Kernel (2) o Schema o table definitions o integrity constraints o views (stored queries) o access control o Stored in Data Dictionary o DD is a Database itself, the System Catalog o Manipulated with DDL and DCL o Factbase o tables o Manipulated with DML o Interface with operating system for file access o Transaction control o concurrency o locking

11 UFCE8K-15-M Data Management 2013/1411 Toolkit - Application Development Tools o e.g. Access o Graphical User Interface (GUI) o QBE to generate SQL queries o Form and report definitions o VB Macros for user programs o Natural Language Interface o translation from natural language to SQL

12 UFCE8K-15-M Data Management 2013/1412 User programs o SQL command line interface o SQLPlus for Oracle, similar for MySQL o Pre-compiler (COBOL..) o Program contains SQL statements which need to be compiled into calls to Kernel functions o Scripts (PHP,Perl) o Generation of SQL calls at runtime

13 UFCE8K-15-M Data Management 2013/1413 CASE tools o e.g. Select SSADM, Rational Rose, Oracle Designer, QSEE, MySQL Workbench, o allow developers to develop schema from ER model o Allows for the generation of SQL DDL for target DB o speeds up development process o reduces costs, especially in maintenance

14 UFCE8K-15-M Data Management 2013/1414 Admin tools o Database software control o starting and stopping Kernel o backup and restore o Reconstruct indexes o Access control o create users, user groups, o assign user access rights to tables o Import and Export of data and schema o Schema migration - major schema change o monitoring and tuning

15 UFCE8K-15-M Data Management 2013/1415 Kernel operations o Underlying file types o Indexing o Transactions o Locks o Rollback o Query optimisation

16 UFCE8K-15-M Data Management 2013/1416 Physical organisation o Secondary storage (on disk) divided into blocks - say 16K in size o For a given file system, blocks have control info(index to records in block..) and free space as well as user records o structured blocks are called ‘pages’ o Data is transferred between main memory and secondary storage in pages o Pages can be held in memory (cached) for speed of access

17 UFIE8K-15-M Data Management 2010/1117 Typical components modules of a DBMS. Dotted lines show accesses that are under the control of the stored data manager

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