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Database Transactions

Database transactions: ACID, isolation levels, MVCC, distributed transactions, sagas, correctness testing and papers.

43 topics•6 categories•Updated October 2026

What Are Database Transactions?

7 entries

A transaction groups several operations into one unit that either fully succeeds or fully fails. Relational databases promise ACID properties (atomicity, consistency, isolation, durability), and isolation levels such as read committed, repeatable read and serializable define what concurrent transactions can observe. Distributed systems add coordination problems that are handled with protocols such as two-phase commit, consensus and sagas. Descriptions below follow each project's or vendor's own pages and are not rankings; release facts come from GitHub.

01Database ReplicationCopying data for availability, on this site. 02Database ShardingSplitting data across servers, on this site. 03Database Performance TuningTuning tools and techniques, on this site. 04Distributed SQL DatabasesScale-out SQL systems, on this site. 05Relational Databases (SQL)PostgreSQL, MySQL and more, on this site. 06Document DatabasesDocument stores with multi-document transactions, on this site. 07Database SystemsDatabase systems hub, on this site.

Transactions in Relational Databases

12 entries

Official documentation on transactions, isolation and concurrency.

08PostgreSQL transaction isolationPostgreSQL documentation on the four standard isolation levels and how PostgreSQL implements them. 09PostgreSQL concurrency control (MVCC)PostgreSQL documentation on multiversion concurrency control, where readers do not block writers. 10PostgreSQL explicit lockingPostgreSQL documentation on table-level, row-level and advisory locks. 11PostgreSQL transactions tutorialIntroductory PostgreSQL tutorial on BEGIN, COMMIT and ROLLBACK. 12PostgreSQL two-phase commitPostgreSQL documentation on PREPARE TRANSACTION for two-phase commit. 13MySQL InnoDB transaction modelMySQL reference manual on the InnoDB transaction model and isolation levels; the MySQL documentation returned 403 to automated checks and may need a manual click. 14MariaDB transactionsMariaDB documentation on transactions. 15SQL Server isolation levelsMicrosoft documentation for SET TRANSACTION ISOLATION LEVEL in T-SQL. 16SQL Server transaction locking and row versioning guideMicrosoft guide to locking and row versioning in SQL Server. 17Oracle data concurrency and consistencyOracle Database 19c documentation on concurrency and consistency. 18SQLite atomic commitSQLite documentation on how it implements atomic commit and rollback. 19SQLite isolationSQLite documentation on isolation between connections.

Transactions in NoSQL Databases

4 entries

What other models guarantee.

20MongoDB transactionsMongoDB documentation on multi-document ACID transactions. 21DynamoDB transactionsAWS documentation on DynamoDB transactional reads and writes. 22Cassandra guaranteesApache Cassandra documentation on its consistency and lightweight transaction guarantees. 23Redis transactionsRedis documentation on MULTI and EXEC transactions.

Distributed Transactions

9 entries

Systems and documentation for transactions across nodes.

24Google Cloud Spanner transactionsGoogle documentation on Spanner transaction types. 25Spanner external consistency and TrueTimeGoogle documentation on external consistency and TrueTime. 26CockroachDB transaction layerCockroach Labs documentation on how CockroachDB implements distributed transactions. 27YugabyteDB transactionsYugabyteDB documentation on its distributed transaction architecture. 28TiDB transaction overviewPingCAP documentation on TiDB transactions. 29FoundationDBApple's open-source distributed database with ACID transactions; its transaction manifesto explains the design argument for transactions. 30Saga pattern (microservices.io)Pattern description: implement transactions across services as a reliably coordinated sequence of local transactions. 31Transactional outbox (microservices.io)Pattern description: write the event to an outbox table in the same transaction, then publish it to a broker. 32TemporalOpen-source durable execution platform often used to implement sagas and long-running workflows.

Correctness Testing and Benchmarking

6 entries

Tools for checking isolation claims and measuring transaction throughput.

33JepsenJepsen describes distributed systems safety research, including analyses of databases' consistency claims. 34Jepsen consistency models mapInteractive map of consistency models such as serializability and snapshot isolation. 35Jepsen analysesPublished analyses of how specific databases behave under faults. 36ElleChecker for transactional isolation violations used with Jepsen. 37TPC-CTransaction Processing Performance Council's OLTP benchmark specification; results are published by vendors and should be read with their disclosures. 38HammerDBOpen-source database benchmarking tool that implements TPC-C-style workloads.

Papers and Explainers

5 entries

Foundational research on isolation and consistency.

39Spanner: Google's Globally Distributed DatabasePaper describing Spanner and its externally consistent distributed transactions. 40Percolator: large-scale incremental processing with distributed transactionsGoogle paper describing transactions over Bigtable that influenced later distributed databases. 41A Critique of ANSI SQL Isolation LevelsMicrosoft Research paper that analysed gaps in the ANSI isolation level definitions; the Microsoft Research page did not return a normal response to automated checks and may need a manual click. 42Highly Available Transactions: Virtues and LimitationsPaper by Bailis et al. on which transactional guarantees can be provided without coordination. 43Linearizability versus serializabilityPeter Bailis's explainer on two often-confused consistency concepts.

Frequently Asked Questions

What does ACID mean?

Atomicity (all or nothing), consistency (constraints hold), isolation (concurrent transactions do not interfere in ways the isolation level forbids) and durability (committed data survives failures).

What are isolation levels?

Settings that define which anomalies concurrent transactions may see: read uncommitted, read committed, repeatable read and serializable in the SQL standard. Databases implement them differently, so PostgreSQL, MySQL, SQL Server and Oracle behave differently at the same named level.

What is MVCC?

Multiversion concurrency control keeps several versions of each row so readers see a consistent snapshot without blocking writers. PostgreSQL, MySQL InnoDB and Oracle use forms of it.

What is the difference between serializability and linearizability?

Serializability is about transactions: the result equals some serial order. Linearizability is about single operations on one object appearing to take effect instantly. Strict serializability combines both. Bailis's explainer covers the difference.

How do distributed transactions work?

Common approaches are two-phase commit coordinated across nodes, consensus-based protocols as in Spanner and CockroachDB, and application-level sagas that use compensating actions. See the Spanner and Percolator papers and the saga pattern.

Do NoSQL databases support transactions?

Some do. MongoDB and DynamoDB offer multi-item ACID transactions, while Cassandra offers lightweight transactions for single partitions and Redis offers MULTI and EXEC. Guarantees and costs differ, so read each product's documentation.

How can I check a database's isolation claims?

Jepsen publishes independent analyses of many databases, and its Elle checker finds isolation violations in recorded histories. Vendor claims are not a substitute for testing your own workload.

How current is this page?

Links and release facts were checked on 31 October 2026. The MySQL documentation returned 403 and the Microsoft Research page did not respond to automated checks. Links that did not resolve were dropped. Descriptions follow each project's own pages and are not rankings.

Where can I learn about database backup and recovery?

See the Database Backup and Recovery page for native backup tools, point-in-time recovery, cloud backup services, Kubernetes backup with Velero and disaster recovery planning.

Where can I learn about database security?

See the Database Security page for access control, encryption, auditing, masking, SQL injection prevention, cloud database security features and hardening guides.