Method and apparatus for maintaining consistency between database and virtual table

A computer program product tangibly embodying computer readable instructions which, when implemented, causes a computer to execute the steps of:

• receiving a request to add an instance of record data to an instance pool of said view;
• judging whether there is a free space for adding said instance in a storage area of said instance pool;
• selecting a discard candidate instance from a discard candidate list table in accordance with a Least Recently Used (LRU) algorithm if it is judged that there is less free space than needed for adding said instance;
• judging whether a revision wait flag is on for said discard candidate instance;
• deleting said discard candidate instance from said discard candidate list table if it is judged that said revision wait flag is on;
• deleting said discard candidate instance from said instance pool and adding said instance to said instance pool if it is judged that said revision wait flag is not on;
• and
• adding said requested instance to said instance pool if it is judged that there is enough of said storage area.

A system for managing a view having a virtual table for a database, said system comprising:

• a view pool containing a retrieval key;
• an instance pool including an instance of at least one part of record data in said database;
• a batch processing part for reflecting said update of a record held in said instance pool to said database;
• and
• means for receiving a request for adding an instance of record data to said instance pool of said view;
• means for judging whether there is a free space for adding said instance in a storage area of said instance pool;
• means for selecting a discard candidate instance from a discard candidate list table in accordance with an Least Recently Used (LRU) algorithm if it is judged that there is less free space for adding said instance;
• means for judging whether a revision wait flag is on for said discard candidate instance;
• means for deleting said discard candidate instance from said discard candidate list table if it is judged that said revision wait flag is on;
• means for deleting said discard candidate instance from said instance pool and adding said instance to said instance pool if it is judged that said revision wait flag is not on;
• and
• means for adding said requested instance to said instance pool if it is judged that there is enough said storage area.