You can use the Linux command split with the option "-l" to split a big file into smaller files by the number of lines/records per output file. "-l" option is for "put NUMBER lines/records per output file".
E.g., If the big file has 1000 records and you want to create five files, you can use the following command:
split -l 200 big_file_name
The above command will create five files: xaa, xab, xac, xad, and xae.
You can find more details about this command by typing "man split" on the terminal.