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), i.e.,
database integrity will be maintained but it is possible that this
transaction may be undone during recovery instead of being redone.
This behavior may be set for an entire Berkeley DB environment as part of the
If a lock is unavailable for any Berkeley DB operation performed in the context
of this transaction, return immediately instead of blocking on the lock.
The error return in the case will be DB_LOCK_NOTGRANTED.
Note: An transaction may not span threads,
i.e., each transaction must begin and end in the same thread, and each
transaction may only be used by a single thread.
Note: cursors may not span transactions, i.e., each cursor must be opened
and closed within a single transaction.
Note: a parent transaction may not issue any Berkeley DB operations, except for
txn_begin, txn_abort and txn_commit, while it has
active child transactions (child transactions that have not yet been
committed or aborted).
The txn_begin function returns a non-zero error value on failure and 0 on success.
The txn_begin function may fail and return a non-zero error for the following conditions:
The maximum number of concurrent transactions has been reached.
The txn_begin function 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 txn_begin function may fail and return
DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail
in the same way.