Data management apparatus and method for efficiently generating a blocked transposed file and converting that file using a stored compression method

A data management apparatus comprising:

• number of records in group determining means for virtual conversion by repeatedly reading at least one record from an input file having a plurality of records, each record including a plurality of fields, adding the at least one record to a buffer, and converting records in the buffer into a post-conversion block on a field-by-field basis until data size of post-conversion blocks for each kind of field of the records in the buffer exceeds a threshold size, wherein the number of records in group determining means determines the number of records of the post-conversion block by counting the records in the buffer, during a process immediately preceding a time when the data size exceeds the threshold size, and stores that number;
• first conversion means for generating a first block by dividing at least one record including a plurality of fields into the fields and combining fields of like kind;
• and
• second conversion means for converting the first block into a second block using a stored data conversion method, and for storing the second block, wherein the second conversion means selects one data compression algorithm that provides highest compression efficiency from a plurality of stored data compression algorithms in accordance with properties of the first block, and converts the first block into the second block using the selected data compression algorithm.