Abstract: An apparatus performs a data migration from a database of a mainframe system to a rehosting solution database of an open system. An unload data set conversion module converts an unload data set, unloaded from the database of the mainframe system, into load files having standard format. A schema information generation module generates a schema information file having conversion rules by segment and field necessary for code system conversion of segment data in the load files having standard format. A code system conversion module converts the load files into load files having a code system of the open system pursuant to the schema information file, wherein the load files. A data load module sequentially reads segment data in the code-converted load files to load the segment data into the rehosting solution database.