s of event journalism before writing (WAL) to ensure integrity of data uses. In summary, the original concept of WAL this is that changes to data files (the location of the storage table, and list) only if should be done when the changes event journalism have been, and records event journalism related in memory, the permanent is recorded. In this case, if the incidence of the bug in the implementation of the database, we can use the events recorded the data to retrieve.