Format conversion of storage data using an efficient division of data

摘要

A database apparatus to realize faster processing for data including a plurality of elements such as objects by conducting the loading and storing process accompanying format conversion only on necessary elements. Objects in storage format in the secondary memory apparatus are written as computable format onto the cache for processing by the application program. In addition, objects in computable format in the cache are written out as storage format on the secondary memory apparatus. A first determination device determines whether invalid or valid elements are contained in at least a portion of the object held in the cache based on status information that is held in the cache. Based on the results of this determination, a second determination device determines which elements in the object are invalid or valid and for invalid elements, the corresponding elements held in storage format are converted to computable format by the loading means and written into the cache while valid elements are converted to storage format by the storage device and written out to the page cache. Furthermore, the reading and writing device writes these out to the secondary memory apparatus.