The MCF message queue file is a file in the OpenTP1 file system and is used when MCF exchanges messages with another system. The MCF message queue file is used as a disk queue for I/O messages: i.e., messages received or messages to be sent. The input queue is used for managing received messages such as requests, and the output queue is used for managing messages to be sent such as processing request results.

OpenTP1 handles MCF message queue files in a logical unit called a queue group, while the actual file that obtains I/O messages is called a physical file. A queue group always consists of one physical file. For each queue, you must create an MCF message queue service definition in which the correspondence between a queue group and a physical file is defined. In the MCF message queue service definition, you can assign any name (ID) to a queue group. Using the queue group ID allows MCF message queue file operation in units of queue groups: for example, you can monitor the percentage of physical files that are used.

In the message queue service definition, you can assign any name (ID) to a queue group. Using the queue group ID, message queue files can be operated as a queue group, when monitoring the usage of physical files, for example.

A queue group can be divided into a number of service groups or logical terminals. Each service group or logical terminal is known as a queue file. The name of the service group or logical terminal is called the queue file name.

Input and output messages are scheduled on the basis of a particular service group or logical terminal, respectively. Dividing a queue group into separate service groups and logical terminals enhances performance when the same resource is being accessed.

Figure 4-13 shows the relationship between queue groups and MCF message queue files.

Figure 4-13 Queue groups and message queue files