DB_TXN *parent, DB_TXN **tid, u_int32_t flags);
The DB_ENV->txn_begin method creates a new transaction in the environment
and copies a pointer to a DB_TXN that uniquely identifies it into
the memory to which tid refers.
Calling the DB_TXN->abort,
DB_TXN->commit or DB_TXN->discard methods will discard the returned
If the parent argument is non-NULL, the new transaction will
be a nested transaction, with the transaction indicated by
parent as its parent. Transactions may be
nested to any level.
In the presence of distributed transactions and two-phase commit,
only the parental transaction, that is a transaction without
a parent specified, should be passed as an argument to
The flags value must be set to 0 or by bitwise inclusively OR'ing together one or
more of the following values:
- All read operations performed by the transaction will read modified but
not yet committed data. Silently ignored if the DB_DIRTY_READ
flag was not specified when the underlying database was opened.
- Do not synchronously flush the log when this transaction commits or
prepares. This means the transaction will exhibit the ACI (atomicity,
consistency, and isolation) properties, but not D (durability); that is,
database integrity will be maintained but it is possible that this
transaction may be undone during recovery.
This behavior may be set for a Berkeley DB environment using the
DB_ENV->set_flags interface. Any value specified in this
interface overrides that setting.
- If a lock is unavailable for any Berkeley DB operation performed in the context
of this transaction,
immediately instead of blocking on the lock.
- Synchronously flush the log when this transaction commits or prepares.
This means the transaction will exhibit all of the ACID (atomicity,
consistency, isolation, and durability) properties.
This behavior is the default for Berkeley DB environments unless the
DB_TXN_NOSYNC flag was specified to the DB_ENV->set_flags
interface. Any value specified in this interface overrides that
Note: A transaction may not span threads; that is, each transaction must
begin and end in the same thread, and each transaction may be used only
by a single thread.
Note: Cursors may not span transactions; that is, each cursor must be
opened and closed within a single transaction.
Note: A parent transaction may not issue any Berkeley DB operations -- except for
DB_ENV->txn_begin, DB_TXN->abort and DB_TXN->commit -- while it has
active child transactions (child transactions that have not yet been
committed or aborted).
The DB_ENV->txn_begin method returns a non-zero error value on failure and 0 on success.
The DB_ENV->txn_begin method may fail and return a non-zero error for the following conditions:
- The maximum number of concurrent transactions has been reached.
The DB_ENV->txn_begin method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB_ENV->txn_begin method may fail and
in which case all subsequent Berkeley DB calls will fail in the same way.
Transaction Subsystem and Related Methods
Copyright Sleepycat Software