non-idempotent

Non-idempotent (at most once) indicates that the remote procedure call cannot be executed more than once because it will return a different value or change a state. Non-idempotent is the default for remote procedure calls.

All non-idempotent calls are executed by the server at most once ; that is, not at all or exactly once. The protocol used to enforce this is the callback function. Non-idempotent requests require the server to perform a callback when it receives a request from a client about which it has no information. The server makes the callback request by issuing a remote procedure call to the client. When it receives the callback, the server s boot time and the client s sequence number are used as the basis of comparison to validate the request. If a match is made, the server executes the original request. Otherwise, the request is ignored.

A non-idempotent call ensures that the data is received and processed at most one time.