Mainframe Access provides comprehensive support for communications between PC clients and mainframe servers. Mainframe Access supports both TCP/IP and LU6.2 protocols. Mainframe Access' ability to bridge client TCP/IP connections to SNA LU6.2 server connections eliminates the need to install, configure and maintain SNA software packages on your client and server workstations. You can even access any DB2 for z/OS and OS/390 database using TCP/IP client connections, without the need for specific levels of DB2 software. Normally, DB2 Version 5.1, or later, is required for TCP/IP access. Mainframe Access, however, dynamically associates TCP/IP client connections with traditional LU6.2 DRDA connections to the DB2 systems.
Mainframe Access has two TCP/IP socket listeners, one for TCP/IP clients using proprietary protocols and one for HTTP clients. The listeners accept client connection requests and examine the request data to determine the target server or internal destination for the request. When the target server is external, the client connection is then associated with an LU6.2 connection to the target server. For each target server type, Mainframe Access creates an initial number of tasks (z/OS TCBs) to handle the client/server connection association and processing. As each connection request arrives, Mainframe Access scans all available tasks for the target server and assigns the new connection request to the task with the lightest load. Mainframe Access' TCP/IP communications support can be used with IBM's z/OS TCP/IP implementation.
When the first client request for an LU6.2 target server is received, Mainframe Access establishes the LU6.2 connection to the target server and negotiates session limits for the mode name associated with conversations (user transactions) to the target server. Mainframe Access then prepares an LU6.2 Function Management Header 5 (FMH-5) and allocates a conversation to the target server. The FMH-5 includes any LU6.2 security subfields (user ID and password) provided by the client and an LUW ID (SNA Logical Unit of Work ID) generated by Mainframe Access to manage the unit of work. Packaged user data to be processed by the transaction program follows the FMH-5. Acceptance of the conversation request by the target server starts the execution of the remote transaction program that will process the request. Response data from the remote transaction program is received by Mainframe Access and returned to the requesting client through the TCP/IP connection. If an LU6.2 communications error occurs during the request processing, Mainframe Access creates a special packet containing the LU6.2 error information and returns this to the requesting client.