A file management program, a file management apparatus, and a file management method are provided which are capable of migrating files between different file systems while an application program is being run.File information of source files on a source file system is acquired and recorded as a file information event, and information of file operations made for the source files are acquired and recorded as a file operation event. Based on the file information event and file operation event, a namespace replication database is generated in which the namespace of the source files has been replicated logically.