The MessageQ MVS Client, Version 3.2, is a client implementation of the MessageQ Application Programming Interface (API). The MVS Client relies on a MessageQ server group to provide complete message queuing. The MVS Client uses an internal request/response protocol to a Client Library Server (CLS) running on a MessageQ server system. The MVS Client is connected to the message queuing bus by a network connection between the MessageQ MVS Client Library and the CLS process in the remote MessageQ server group.
The CLS is a MessageQ application that runs as a background server to handle multiple MVS Client connections. The CLS performs all communication with the MVS Client application until the application detaches from the message queuing bus. The message queue operations and network activities of each client are isolated from other clients.
The CLS acts as a remote agent to perform MessageQ message functions in the MessageQ server group on behalf of the MVS Client. The MVS Client Library establishes a network connection to the CLS when an application initiates an attach queue operation. The connection to the CLS is closed when the application performs a detach queue operation.
The MessageQ MVS Client Library allows multiple applications to connect to separate queues on the message queuing bus. This library creates a separate network connection to the CLS for each application using MessageQ. The total number of applications that can connect to the message queuing bus is limited by the number of TCP/IP sessions.
The MVS Client provides a local store-and-forward (SAF) journal to store recoverable messages when the connection to the CLS is not available. When the connection to the CLS is reestablished, all messages in the SAF journal are sent before new messages are processed.
The MessageQ MVS Client provides application developers a means to integrate their MVS mainframe environments with distributed heterogeneous systems through the use of MessageQ message queuing middleware. The MessageQ MVS Client, with support for MVS CICS and MVS batch, provides guaranteed message delivery between IBM mainframe applications and others running on any MessageQ supported platforms by means of a direct TCP/IP network connection.
The MessageQ MVS Client allows users to make MessageQ calls from MVS mainframe applications, providing customers the ability to use a single API for all application environments. The wide range of platforms covered by MessageQ offers developers a single, consistent programming interface to develop and deploy distributed applications across the entire spectrum of enterprise systems, including Microsoft Windows 95 desktops, Windows NT, all popular UNIX variants, OpenVMS, and IBM MVS mainframe environments.
The MessageQ MVS Client can host its communications capabilities on a MessageQ server implementation residing on any node in the network. The value of off-loading the MessageQ communications capability to a non-IBM MVS node, while making MessageQ calls and offering a recoverable link from the MVS environment, is important for companies looking to integrate the applications running on their MVS mainframes with applications running on UNIX, OpenVMS, and Windows NT servers.