Abstract: A method and apparatus for coordinating activities of data base management systems operable on Closely-Coupled Host Processors. In particular, messages can be quickly passed between data base management systems executing on Host Processors which are coupled to a Record Lock Processor. One or more receiver processes register with the operating system to receive messages. When the operating system detects a message a Receiver Process begins processing the message. When a data base management system detects that other data base management systems should be notified of an event, a message sending interface is called with a parameter which indicates particular Host Processors and a parameter containing the message to send, and the message is sent to the Host Processors specified. Programs sending messages may elect to have execution suspended until a response message is received from the other Host Processors.