Services of dbms
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This document provides an overview of key database concepts including database security, recovery, data integrity, transaction support, and concurrency control. It describes common security mechanisms like authentication and authorization. It also outlines database recovery mechanisms like backups and change log maintenance. Data integrity and constraints are discussed. Transaction support services that allow committing or rolling back transactions are covered. Finally, it defines concurrency control and locking mechanisms used to prevent data inconsistencies between concurrent transactions.
Services of dbms
- 1. Muhammad Umair Oracle Database 11g Developer Track
- 2. › Database Security › Database Recovery › Data Integrity › Transaction Support › Concurrency Control
- 3. › Database Security – DBMS furnishes mechanisms to prevent data from accidental or intentional looses, destruction or misuse. – Two of common security mechanisms are: › Authentication – DBMS requires people to prove their identity before connecting to the database › Authorization – DMBS enable developers to define right or privileges of the database users
- 4. › Database Recovery – DBMS furnishes mechanisms to restore data efficiently and accurately after any type of loss od damage – Two of the recovery mechanisms are: › Back-up – A copy of database is maintained to be use for recovery in case of damage of the whole or some of its parts › Change-log Maintenance – The changes mage to the data are recorded so that data may be restored to some of its previous state.
- 5. › Data Integrity – DBMS furnishes mechanisms to ensure that only valid data in entered into the database › Data integrity mechanisms: – Enable developers to define constraints on data. – Enable developers to create code segments to ensure validity of data before or after some DML statements for example triggers
- 6. › Transection Support Service – DBMS furnishes mechanisms to ensure that either all updates included in a transaction are made or none of them is made. – As part of transection support mechanisms DBMS let user to commit or rollback their transactions
- 7. › Concurrency Control Service – DBMS furnishes mechanisms to prevent from data inconsistency when two or more transaction occurs same data at same time. › Locking Mechanism – A resource accessed by a transaction is banned for other transaction until that transaction completed. – There are two types of locks – Shared Lock › A lock that is applied for readers. It can be shared by many transaction – Exclusive Lock › A lock that is applied for writers. It cant be shared by different transaction
- 8. › Dead Lock – A situation in which locks don’t resolve by automatic process, until DBMS takes special action for their resolution – In a database, a deadlock is a situation in which two or more transactions are waiting for one another to give up locks. For example, Transaction A might hold a lock on some rows in the Accounts table and needs to update some rows in the Orders table to finish