Comparison of the Speed of the Access and Storage Requirements for Different File Types

Storage Requirements

  • Sequential and Direct access files are the same size, however Indexed files require more space because of the storage of the index
    • In a large system the index file could, for 1,000,000 file take up over 10,000,000 Bytes

Speed is vitally dependent on:
  • The Access Time to a Hard Disk
  • The Access Time to read an index file
  • The access Time to read tapes or other forms of media

Speed Comparrsion

  • Sequential Access is the slowest form since it has to read all the data preceding the file that should be accessed. This can mean that all files have to be read if the file required is stored last
  • Index Access is faster since it only requires to read the entire index and can then simply skip forward to the file requred.
  • Record Accessis the potentially fastest but is also affected by the amount of logical records stored in a physical record.
    • This means that the more records are blocked into a physical record, the less time is required to access the required file.

Created by: Daniel Gillo
Last modification: 15th September 2011

  • Jones, Richard. Computer Science Java Enabled. Victoria: IBID Press, 2004