DBMS[1].pptx HELPS IN DATABASE MANAGEMNT SYSTEM

DBMS ERROR RECOVERY

1. error recovery and logging. undo , redo, undo-redo logging and recovery methods. PRESENTED BY: BORIGI SHREEKA-230101120153 KONISHA TRILOK-230101120154 SANJAYA KUMAR PANDA-230101120155 RUDRA LENKA-230101120156 YAJNADATTA PATTANAYAK-230101120157 SUBMITTED TO : Prof. SAGARIKA DASH

2. INTRODUCTION UNDO AND REDO UNDO-REDO LOGGING RECOVERY METHODS CHECKPOINTING ARIES RECOVERY SYSTEM ADDITIONAL POINTS CASE STUDIES FUTURE TRENDS BENEFITS CONCLUSION CONTENTS

3. In a database management system (DBMS), error recovery and logging uses a redo/undo recovery algorithm to undo incomplete transactions and redo completed ones when a failure occurs. The algorithm uses the transaction log to determine which transactions were incomplete at the time of the failure. Introduction to Error Recovery

4. Undo and Redo Operations: UNDO: This involves reversing the changes made by an incomplete transaction (one that hasn't been committed) due to a crash. The system uses the transaction log, which keeps track of all database modifications, to identify these uncommitted changes and revert them. REDO: This ensures that all committed transactions (ones that successfully completed) are reflected in the database even after a crash. The log helps identify these transactions, and the system replays the changes they made to bring the database to a consistent state.

5. Undo-redo logging is a combined approach that incorporates both undo and redo logging techniques for recovery. It provides a more robust recovery mechanism by allowing for both rollback and redo operations during recovery. Undo-redo logging ensures that transactions can be efficiently rolled back or redone to maintain data consistency and recover from failures effectively. Undo-Redo Logging

6. Recovery Methods Crash Recovery: Crash recovery is the process of restoring a database to a consistent state after a system crash or failure. It typically involves replaying logged operations from the log to redo or undo incomplete transactions. Media Recovery: Media recovery is the process of restoring a database after a disk failure or corruption. It involves restoring data from backups or using log-based recovery techniques to recover lost or damaged data.

7. Checkpointing: This is an optimization technique used alongside redo-undo logging. At specific points in time, the system takes a checkpoint, which is a snapshot of the consistent database state along with the log position up to that point. During recovery, the system can start from the latest checkpoint, reducing the amount of log required for redo/undo operations.

8. ARIES Recovery Algorithm ARIES (Algorithm for Recovery and Isolation Exploiting Semantics) is a widely used recovery algorithm in DBMS. It provides efficient crash recovery and supports concurrency control mechanisms like locking and timestamp ordering. ARIES consists of three main components: Analysis, Redo, and Undo. It ensures that transactions are properly committed or rolled back during recovery, maintaining database consistency and integrity.

9. Here are some additional points to consider: Idempotence: Both undo and redo operations should be idempotent, meaning repeated applications have the same effect as a single application. This ensures data integrity during recovery. Durability: The transaction log entries must be written to stable storage before the corresponding database modifications occur. This guarantees that the log reflects the actual state of the database.

10. Case Studies Real-world examples of error recovery and logging in popular DBMS platforms, such as Oracle, MySQL, and PostgreSQL, demonstrate the application of these concepts in ensuring data integrity and system reliability. Future Trends Emerging technologies and trends in error recovery and logging in DBMS, such as distributed logging and cloud-based recovery solutions, are shaping the future of data management and system resilience.

11. Benefits OF ERROR RECOVERY : Data Integrity: Ensures data remains unaltered and reflects the intended state after failures. Data Availability: Minimizes downtime by enabling recovery and resuming database operations quickly. Maintain Consistency: Guarantees the database adheres to its defined rules and relationships between data elements.

12. Conclusion By employing error recovery and logging techniques, DBMSs can maintain data integrity and minimize the impact of system failures.

13. Thank you very much