Sun Java System Message Queue 4.3 Developer's Guide for C Clients

Flow Control

A number of connection properties determine the use of Message Queue control messages by the client runtime. Messages sent and received by Message Queue clients and Message Queue control messages pass over the same client-broker connection. Because of this, delays may occur in the delivery of control messages, such as broker acknowledgements, if these are held up by the delivery of JMS messages. To prevent this type of congestion, Message Queue meters the flow of JMS messages across a connection.

You should keep the value of MQ_CONNECTION_FLOW_COUNT_PROPERTY low if the client is doing operations that require many responses from the broker; for example, the client is using the CLIENT_ACKNOWLEDGE or AUTO_ACKNOWLEDGE modes, persistent messages, transactions, or if the client is adding or removing consumers. You can increase the value of MQ_CONNECTION_FLOW_COUNT_PROPERTY without compromising performance if the client has only simple consumers on a connection using DUPS_OK mode.

The C API does not currently support consumer-based flow control.