Oracle Rdb saves and allows you to access up to 20 of your most
    recently entered RDO commands. Use the UP-ARROW or CTRL/B keys
    to recall previously entered commands. Use the DOWN-ARROW key
    to reexamine a command that you had retrieved using the UP-ARROW
    key.

    This feature is designed for the convenience of RDO users. It
    greatly reduces the need to enter the RDO editing buffer to
    rerun one or more of your last 20 commands. The EDIT statement
    continues to be a useful tool for created RDO procedures in that
    it lets you take advantage of your editor's text manipulation
    features and it lets you edit multiple lines.