Posted January 21, 2008on:
Refers to an operation that produces the same results no matter how many times it is performed. For example, if a request to delete a file is successfully completed for one program, all subsequent requests to delete that file from other programs would return the same success confirmation message if the delete function were idempotent. In a function that is not idempotent, an error would be returned for the second and subsequent requests indicating that the file was not there, and that error condition might cause the program to halt. If all that were desired was to ensure a certain file was deleted, an idempotent delete function would return the same success result no matter how many times it was executed for the same file.