Return true if there is an active transaction.
Begin a transaction in the current fiber.
A transaction is attached to caller fiber, therefore one fiber can have only one active transaction. See also box.begin().
Returns: 0 on success Returns: -1 on error. Perhaps a transaction has already been started.
Commit the current transaction. See also box.commit().
Returns: 0 on success Returns: -1 on error. Perhaps a disk write failure
Return a descriptor of a savepoint.
Roll back the current transaction as far as the specified savepoint.
Allocate memory on txn memory pool.
The memory is automatically deallocated when the transaction is committed or rolled back.
Returns: NULL on out of memory