File system with file management function and file management method

A file management method for use in a file system with a transaction management function comprising:

• allocating a file area and a temporary write area in a storage area of a storage unit, the file area storing files each having pages, the temporary write area being used to temporarily store update data in units of pages of the files;
• acquiring an unused page from the temporary write area when a request to update a page included in the files stored in the file area is issued:
• updating the page by writing updated data to the unused page acquired from the temporary write area;
• copying data of one of a pair of map tables to the other of the pair of map tables when a transaction is committed, the pair of map tables being used to record a list of effective pages included in the temporal write area and updated, the one of the pair of map tables being used to record the list when a previous transaction is committed, the other map table being not used to record the list when the previous transaction is committed;
• recording, in the one map table, a list of current effective pages in the temporary write area;
• and
• performing real update processing for writing back, to original page positions in the file area, the updated data of the effective pages in the temporary write area, the real update processing including release of the effective pages after the updated data of the effective pages is written back to the original page positions.