BeginTransaction

Begin transaction (often exposed as beginTransaction) is a database operation that starts a new transaction. A transaction groups a set of data-modifying operations so that they either all succeed together or have no effect if rolled back. When a transaction begins, the database typically disables autocommit for the session and establishes a transactional scope that persists until a COMMIT or ROLLBACK is issued.

SQL standards describe beginning a transaction with BEGIN TRANSACTION (or BEGIN), with some dialects using START TRANSACTION. The exact syntax varies by database system (for example, BEGIN TRANSACTION in SQL Server and SQLite, BEGIN in PostgreSQL and MySQL as equivalent).

In application code, beginTransaction is commonly provided as a method on a connection or database context. It returns a transaction object that can later be committed or rolled back. Examples include JDBC: for begin, setAutoCommit(false) on a Connection, then call commit() or rollback(); EF Core: context.Database.BeginTransaction(); SQLAlchemy: session.begin().

Transactions rely on ACID properties: atomicity, consistency, isolation, durability. They offer control over isolation level, which determines visibility of changes during the transaction. Some systems support savepoints to roll back to a sub-transaction within a larger one. Long-running transactions or those that hold locks can cause contention and deadlocks.

See also: commit, rollback, savepoint, autocommit, isolation level, two-phase commit.