This message is sent by an account owner to an account servicer (account servicing institution). The account owner may be a global custodian which has an account with its local agent (sub-custodian) or an investment management institution or a broker/dealer which has an account with their custodian.
This message is used to instruct the movement of securities within its holding, eg, re-registration of securities. It is not to be used for collateral management.