ARIES 편집하기

'''ARIES (Algorithm for Recovery and Isolation Exploiting Semantics)''' is a robust and efficient algorithm used for transaction recovery in database management systems (DBMS). Developed by C. Mohan and his colleagues, ARIES ensures '''atomicity''' and '''durability''' properties of transactions by providing a framework for '''undoing''', '''redoing''', and '''recovering''' database operations in the event of a crash or failure.
==Key Features of ARIES==
*'''Write-Ahead Logging (WAL):''' Ensures that log entries are written to stable storage before corresponding changes are applied to the database.
*'''Physiological Logging:''' Combines physical and logical logging to optimize recovery performance.
*'''Three-Phase Recovery Process:''' Uses analysis, redo, and undo phases for efficient crash recovery.
*'''Support for Partial Rollbacks:''' Handles nested transactions and partial rollbacks effectively.
*'''Flexible Checkpointing:''' Reduces recovery time by periodically saving the state of the database.
==Phases of the ARIES Algorithm==
The ARIES recovery process consists of three main phases:
===Analysis Phase===
*Scans the log to determine the state of transactions and dirty pages (pages modified but not written to disk) at the time of the crash.
*Reconstructs the transaction table and dirty page table to facilitate the subsequent phases.
===Redo Phase===
*Reapplies all changes from the log to ensure that the database reflects the most recent committed state.
*Starts from the earliest point where a change to the dirty pages occurred, identified during the analysis phase.
===Undo Phase===
*Reverts changes made by uncommitted transactions by traversing the log backward.
*Uses compensation log records (CLRs) to ensure idempotency, allowing the undo phase to be restarted if interrupted.
==Advantages of ARIES==
*'''Efficiency:''' Combines physical and logical logging for faster recovery.
*'''Crash Robustness:''' Guarantees database consistency even after system crashes.
*'''Support for Concurrency:''' Works seamlessly with concurrent transactions.
*'''Scalability:''' Handles large datasets and high transaction volumes effectively.
==Limitations of ARIES==
*'''Complexity:''' Implementation of ARIES is intricate and requires careful design.
*'''Disk I/O Overhead:''' Frequent logging and checkpointing can increase disk I/O.
*'''Dependency on Log Integrity:''' Relies heavily on the correctness and availability of logs for recovery.
==Applications of ARIES==
ARIES is widely used in relational database management systems (RDBMS) and other transactional systems:
*'''Enterprise Databases:''' Oracle, IBM Db2, and SQL Server use recovery mechanisms inspired by ARIES.
*'''Banking Systems:''' Ensures durability and consistency for financial transactions.
*'''Cloud Databases:''' Provides reliable recovery for distributed database systems.
== Example of ARIES Workflow ==
# A transaction modifies the database:
#* Log entries are written for the changes (WAL ensures logs are stored first).
#* Changes are applied to the database.
# The system crashes before committing the transaction:
#* During recovery, the analysis phase determines the state of transactions and dirty pages.
#* The redo phase reapplies committed changes to ensure durability.
#* The undo phase rolls back uncommitted changes to maintain consistency.

== Applications of ARIES ==
ARIES is widely used in relational database management systems (RDBMS) and other transactional systems:
* '''Enterprise Databases:''' Systems like IBM Db2, Oracle Database, and Microsoft SQL Server implement recovery mechanisms based on ARIES.
* '''PostgreSQL:''' While not implementing ARIES directly, PostgreSQL uses similar principles in its WAL-based recovery process.
* '''MySQL (InnoDB):''' InnoDB storage engine leverages concepts inspired by ARIES for its crash recovery.
* '''Distributed Databases:''' Distributed systems like Google Spanner and Amazon Aurora incorporate techniques influenced by ARIES to ensure consistency and reliability.
==Related Concepts and See Also==
*[[Write-Ahead Logging]]
*[[Transaction Management]]
*[[Checkpointing]]
*[[Database Recovery]]
*[[Two-Phase Commit]]
*[[Durability (ACID)]]
*[[Concurrency Control]]
[[Category:Database]]
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