File Manager
File manager handles the allocation of space on disk storage. It starts and maintains the list of structures and indices described in the internal schema that is used to show information stored on disk. Therefore, the file manager does not directly manage the input of data and physical output. It passes the requests on to the suitable access methods, which either write data or read data from into the system cache or buffer. The file manager can be executed using an interface to the existing file subsystem given by the operating system of the host computer or it can have a file subsystem written especially for the DBMS.