Database Normalization and Transaction Management: A Comprehensive Guide

Posted on May 7, 2024 in Computers

Understanding Database Normalization

Goals of Normalization

Normalization is a crucial process in database design aimed at organizing data efficiently and minimizing redundancy. Its primary goals include:

  • Minimizing Data Redundancy: Eliminating duplicate data to save storage space and ensure consistency.
  • Ensuring Data Integrity: Maintaining data accuracy and consistency through logical organization and redundancy reduction.

Advantages of Normalization

Implementing normalization offers several benefits, such as:

  • Improved Data Organization: Data is structured into logical units, enhancing clarity and manageability.
  • Increased Flexibility: Normalized databases adapt better to changing requirements and data structures.
  • Enhanced Performance: Reduced redundancy leads to faster data storage and retrieval, improving overall performance.

Database Management System (DBMS) Failures

DBMS failures can arise from various sources, including hardware malfunctions, software errors, and network issues. Common types of failures include:

Transaction Failures

  • Logical Errors: Violations of database integrity constraints, such as inserting duplicate keys.
  • System Errors: Problems within the DBMS itself, like deadlocks or resource limitations.
  • User Errors: Incorrect data input or improper operation execution by users.

System Failures

  • Hardware Failures: Issues with physical components, such as disk failures, power outages, or network disruptions.
  • Software Failures: Bugs or errors in software, including the DBMS or related system software.

Network Failures

  • Communication Errors: Problems with network connections between clients and servers, leading to timeouts, packet loss, or connection drops.

Concurrency Control and Two-Phase Locking (2PL)

Concurrency control mechanisms ensure data consistency when multiple transactions access the database simultaneously. The Two-Phase Locking (2PL) protocol is a popular method to achieve serializability.

Phases of 2PL

  1. Growing Phase: Transactions acquire locks on data items but cannot release any.
  2. Shrinking Phase: Transactions release locks but cannot acquire new ones.

Guaranteeing Serializability

2PL ensures serializability by preventing conflicts between transactions through lock acquisition and release. Strict 2PL further guarantees serializability by adhering to a specific order of lock release.

Transaction States and ACID Properties

Transaction States

A transaction progresses through various states during its lifecycle:

  1. Active: Transaction execution begins.
  2. Blocked: Transaction waits for a lock held by another transaction.
  3. Ready: Transaction has acquired all necessary locks and awaits CPU time.
  4. Executing: Transaction performs read and write operations.
  5. Partially Committed: Transaction operations are complete, but changes are not yet permanent.
  6. Committed: Transaction changes are permanently saved and visible to other transactions.

ACID Properties

ACID properties ensure reliable and consistent transaction processing:

  • Atomicity: Transactions are treated as a single unit, either fully completed or fully rolled back.
  • Consistency: Transactions maintain database consistency before and after execution.
  • Isolation: Concurrent transactions execute independently without interference.
  • Durability: Committed transaction changes are permanent and survive system failures.

Transaction Processing Systems (TPS) and Transaction Control Language (TCL)

Transaction Processing Systems (TPS)

TPSs manage routine transactions within organizations, ensuring efficiency, accuracy, and security.

Transaction Control Language (TCL)

TCL commands control transactional behavior in a DBMS:

  • COMMIT: Permanently saves transaction changes to the database.
  • ROLLBACK: Undoes transaction changes and restores the database to its previous state.
  • SAVEPOINT: Marks a point within a transaction for potential rollback.

Keys in Relational Databases

Types of Keys

  • Candidate Key: A minimal set of attributes uniquely identifying each tuple in a relation.
  • Primary Key: A chosen candidate key designated as the main identifier for records in a table.
  • Foreign Key: An attribute referencing the primary key of another relation, establishing relationships between tables.

Functional Dependencies (FDs) and Dependency Preservation

Functional Dependencies (FDs)

FDs describe how the value of one attribute determines the value of another attribute(s) in a relation.

Dependency Preservation

Dependency preservation ensures that all FDs in the original relation are maintained in the decomposed relations during normalization.

Conflict Serializability and Timestamp-based Protocol

Conflict Serializability

Ensures database consistency regardless of transaction execution order, as long as conflicting operations are serialized.

Timestamp-based Protocol

Assigns timestamps to transactions to determine their relative precedence and resolve conflicts.

By understanding these concepts, you can effectively design and manage databases, ensuring data integrity, consistency, and efficient transaction processing.