Database Integrity, Security and Recovery Database integrity Database integrity Database security Database security Database recovery Database recovery

Database Integrity Database integrity – refers to correct processing of a database such as applying the appropriate business rules when performing a database operations Database integrity – refers to correct processing of a database such as applying the appropriate business rules when performing a database operations Means that data stored in a database are accurate Means that data stored in a database are accurate

Several ways to ensure data integrity: Several ways to ensure data integrity: Domain integrity Domain integrity Entity integrity constraint Entity integrity constraint Referential integrity Referential integrity Business rules Business rules Database consistency Database consistency Database Integrity

Domain integrity Domain integrity Means entries in a field or column from the same domain Means entries in a field or column from the same domain Validation rules can be applied to trap errors Validation rules can be applied to trap errors Entity integrity constraint Entity integrity constraint Each row in a relation must be unique Each row in a relation must be unique Primary key shows the uniqueness of a rows, cannot be NULL (called entity integrity constraint) Primary key shows the uniqueness of a rows, cannot be NULL (called entity integrity constraint) Referential integrity Referential integrity Means that if a table has a foreign key, then a rows of the key must be exist in the referenced table Means that if a table has a foreign key, then a rows of the key must be exist in the referenced table Database Integrity

Business rules Business rules Relationship between entities define the business rules Relationship between entities define the business rules Database consistency Database consistency Must be consistent before and after a transaction Must be consistent before and after a transaction All database integrity constraints are satisfied All database integrity constraints are satisfied Database Integrity

All data must be protected from all types of threats All data must be protected from all types of threats Accidental threats – caused by accidents such as operator carelessness, power failure, disk crashes and fire. Accidental threats – caused by accidents such as operator carelessness, power failure, disk crashes and fire. Intentional – caused by human, to exploit weaknesses in the system for personal gain. Such as unauthorized access to database Intentional – caused by human, to exploit weaknesses in the system for personal gain. Such as unauthorized access to database Database Security

Security measures Security measures Views/subschemas Views/subschemas Authorization rules Authorization rules Authentication Authentication Encryption Encryption User-defined procedures User-defined procedures Database Security

Views/subschemas Views/subschemas Different user has a different views. Different user has a different views. Corresponds to a subset of the database presented to the user Corresponds to a subset of the database presented to the user Authorization rules Authorization rules To restrict access to data and operations To restrict access to data and operations Authentications Authentications Using a specific device to detect personal characteristic Using a specific device to detect personal characteristic Database Security

Encryption Encryption Used to protect highly confidential or sensitive data Used to protect highly confidential or sensitive data Coding or scrambling data to unintelligible form Coding or scrambling data to unintelligible form Data must be decrypt before the receiver read it Data must be decrypt before the receiver read it User-defined procedures User-defined procedures Users write their own procedures to protect data Users write their own procedures to protect data Database Security

Several approaches to recover from system failures Several approaches to recover from system failures Backup failure – makes a copies of the database Backup failure – makes a copies of the database Journalizing facilities – used to store the audit trails of transactions and database changes Journalizing facilities – used to store the audit trails of transactions and database changes Checkpoint facilities – will refuse to accept any new transaction Checkpoint facilities – will refuse to accept any new transaction Recovery manager – restore the database correctly after a failure has occured Recovery manager – restore the database correctly after a failure has occured Database Recovery

Types of database failure Types of database failure Aborted transaction – to correct the errors, the system must roll back by undoing the steps for the transaction Aborted transaction – to correct the errors, the system must roll back by undoing the steps for the transaction Incorrect data – updating a database correctly but with uncorrect data Incorrect data – updating a database correctly but with uncorrect data System failure – power failure, disk crashed System failure – power failure, disk crashed Database destruction – part of database may be destroyed Database destruction – part of database may be destroyed Database Recovery

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