Connecting CICS systems

Part of the installation of DQM requires the definition and installation of CICS logical unit type 6.2 (LU 6.2) connections that provide the physical link between the CICS systems serving the local queue manager, and the systems serving the remote queue managers. To set up these connections, use the CICS Intercommunication Guide.

One z/OS system can be host to a number of CICS systems at the same time, and each CICS system is able to connect to one queue manager at any one time.

You provide communication links so that queue managers may use these links, through CICS intersystem communication (ISC) to reach other queue managers on z/OS systems (using CICS or not), and on other non-z/OS systems, provided they are using the standard queue manager intercommunication protocol, WebSphere MQ Message Channel Protocol.

Communication between queue managers

There are two forms of communication between CICS systems:

• Intersystem communication (ISC): communication between a CICS system and other systems in a data communication network that support the logical unit type 6.1 or logical unit type 6.2 protocols of IBM Systems Network Architecture (SNA).
• Multiregion operation (MRO): communication between CICS systems running in different address spaces of the same z/OS system.

Only ISC LU 6.2 protocols are used for connecting two queue managers over a DQM channel, even where they both reside in the same z/OS system.

Note:

CICS for MVS/ESA Version 4 Release 1.0 or higher is required for WebSphere MQ distributed queue management.

Intersystem communication

The connection type must be ISC LU 6.2, but can be defined as one of the following:

• LU 6.2 single-session terminal
• LU 6.2 single-session connection
• LU 6.2 parallel-session connection

Before deciding the type of connection to be defined, you should consider the following points:

• The number of channels to be defined between the two systems
• The maximum number of channels that are to be active at any one time
• How often the connection is used
• The number of channels per transmission queue
• The number of channels that can be active per connection

Note:

Multiple channels can be active on the same connection.

To define an LU 6.2 link between the two CICS systems, you should refer to the following books:

• CICS Intercommunication Guide, SC33-1695.
• CICS Resource Definition Guide, SC33-1684.

paying particular attention to the sections discussing communication resources.