Start new transaction scope and sets AutoCommit to false. Followed data changes will be visible only by the current connection, until, Commit() is executed. Executing Rollback() will undo all changes that was made after begin current transaction. The behaviour is similiar to BEGIN TRANSACTION SQL statememnt.

public: void BeginTransaction(
    const TRAN_ISOLATION_LEVEL iso_level = READ_COMMITTED
);

public void BeginTransaction(
    const TRAN_ISOLATION_LEVEL iso_level
);

Public Function BeginTransaction(
    iso_level As const TRAN_ISOLATION_LEVEL = READ_COMMITTED
) As void

If server sends back to the client the error, node_exception exception, containing the error message, will be thrown