One place where these files are useful is for files with holes in them. In UNIX, a process can create a file and write 1 byte into it, then seek to byte 1 billion and write a second byte. On the disk, only two blocks are used, but most file transfer protocols would send the file as 1,000,000,001 bytes. With paged files this can be avoided. Paged file are also used to indicate that some pages may contain bad data due to magnetic tape read errors or measuring instrument problems.
File transfer can occur in three different modes.
Stream mode is used for ordinary files. Compressed mode us used to squeeze out runs of consecutive characters, typically spaces, in record-oriented files. Block mode is used for paged files, in which each page has its own header. Checkpointing and error recovery it provided for compressed and block mode files. Some of them have to do with sending and receiving files.