(1) In SNA, a record that contains control information for the data that follows.
(2) One or more headers, optionally present in the leading request units (RUs) of an RU chain, that allow one LU to (a) select a transaction programme or device at the session partner and control the way in which the end-user data it sends is handled at the destination, (b) change the destination or the characteristics of the data during the session, and (c) transmit between session partners status or user information about the destination (for example, a programme or device). Function management headers can be used with LU type 1, 4, and 6.2 protocols.