The transaction subsystem makes operations atomic, consistent, isolated, and durable in the face of system and application failures. The subsystem requires that the data be properly logged and locked in order to attain these properties. Berkeley DB contains all the components necessary to transaction-protect the Berkeley DB access methods and other forms of data may be protected if they are logged and locked appropriately.
The transaction subsystem is created, initialized, and opened by calls to BDB::Env#open with the BDB::INIT_TXN flag (or BDB::INIT_TRANSACTION) specified. Note that enabling transactions automatically enables logging, but does not enable locking, as a single thread of control that needed atomicity and recoverability would not require it.
The transaction is created with BDB::Env#begin or with begin