Control-Y is a common computer command. It is generated by pressing the Y Key at the same time as the Control key on most Computer Keyboards.
In graphical user interface environments that use the control key to control the active program, control-Y is often used to redo actions.
In specific applications
⌘ Command+Y usually does not have this meaning in the Apple Macintosh operating system, where ⇧ Shift+⌘ Command+Z often does it.
For Linux programs, Control+Y usually does nothing or functions as redo. In many applications, redo is handled by ⇧ Shift+Control+Z.
In emacs, Control+Y does a paste action (known as "yank").
In vi and vim Control+Y scrolls the page up, line by line.
In the pico and nano text editors shortcut scrolls one page up.
In SAPgui Control+Y enters block-select mode, allowing the user to select text from a fixed-width text output such as an ABAP report. The mouse cursor turns into a cross-hair and the user can drag it across some text in order to select it (text in reports is not selectable across vertical text lines in SAPGui).
In Microsoft Office this keyboard shortcut functions as redo: it repeats the previous action.