Intercommunication

Getting started with objects

Use the WebSphere MQ commands (MQSC) or the WebSphere MQ Explorer on Windows systems to:

Define message channels and associated objects
Monitor and control message channels

The objects you may need to define are:

Transmission queues
Remote queue definitions
Queue manager alias definitions
Reply-to queue alias definitions
Reply-to local queues
Processes for triggering (MCAs)
Message channel definitions

Channels must be completely defined, and their associated objects must exist and be available for use, before a channel can be started. This chapter shows you how to do this.

In addition, the particular communication link for each channel must be defined and available before a channel can be run. For a description of how LU 6.2, TCP/IP, NetBIOS, SPX, and DECnet links are defined, see the particular communication guide for your installation. See also the example configuration chapters in this book.

Creating objects

Use MQSC to create the queue and alias objects: transmission queues, remote queue definitions, queue manager alias definitions, reply-to queue alias definitions, and reply-to local queues.

Also create the definitions of processes for triggering (MCAs) in a similar way.

For an example showing how to create all the required objects see Chapter 21, Message channel planning example for distributed platforms.

Creating default objects

In WebSphere MQ for AIX, iSeries, HP-UX, Linux, Solaris, and Windows systems, and MQSeries V5.1 for Compaq Tru64 UNIX, and OS/2 Warp, default objects are created automatically when a queue manager is created. These objects are queues, channels, a process definition, and administration queues. They correspond to the objects that are created when you run the amqscoma.tst sample command file on earlier releases of these products and on other WebSphere MQ products.

How are default objects created?

When you use the CRTMQM command to create a queue manager, the command also initiates a program to create a set of default objects.

Each default object is created in turn. The program keeps a count of how many objects are successfully defined, how many already existed and were replaced, and how many unsuccessful attempts there were.
The program displays the results to you and if any errors occurred, directs you to the appropriate error log for details.

When the program has finished running, you can use the STRMQM command to start the queue manager.

See the WebSphere MQ System Administration Guide book for information about the CRTMQM and STRMQM commands and a list of default objects.

Changing the default objects

Once the default objects have been created, you can replace them at any time by running the STRMQM command with the -c option. When you specify the -c option, the queue manager is started temporarily while the objects are created and is then shut down again. You must use the STRMQM command again, without the -c option, if you want to start the queue manager.

If you wish to make any changes to the default objects, you can create your own version of the old amqscoma.tst file and edit it.

Creating a channel

To create a new channel you have to create two channel definitions, one at each end of the connection. You create the first channel definition at the first queue manager. Then you create the second channel definition at the second queue manager, on the other end of the link.

Both ends must be defined using the same channel name. The two ends must have compatible channel types, for example: Sender and Receiver.

To create a channel definition for one end of the link use the MQSC command DEFINE CHANNEL. Include the name of the channel, the channel type for this end of the connection, a connection name, a description (if required), the name of the transmission queue (if required), and the transmission protocol. Also include any other attributes that you want to be different from the system default values for the required channel type, using the information you have gathered previously.

You are provided with help in deciding on the values of the channel attributes in Chapter 6, Channel attributes.

Note:: You are very strongly recommended to name all the channels in your network uniquely. Including the source and target queue manager names in the channel name is a good way to do this.

Create channel example

DEFINE CHANNEL(QM1.TO.QM2) CHLTYPE(SDR) +
DESCR('Sender channel to QM2') +
CONNAME(QM2) TRPTYPE(TCP) XMITQ(QM2) CONVERT(YES)

In all the examples of MQSC the command is shown as it would appear in a file of commands, and as it would be typed in OS/2, Windows NT, UNIX systems, Compaq OpenVMS Alpha, or Compaq NonStop Kernel. The two methods look identical, except that to issue a command interactively, you must first start an MQSC session. Type runmqsc, for the default queue manager, or runmqsc qmname where QMNAME is the name of the required queue manager. Then type any number of commands, as shown in the examples.

For portability, you should restrict the line length of your commands to 72 characters. Use a concatenation character as shown to continue over more than one line. On Compaq NonStop Kernel, use Ctrl-y to end the input at the command line, or enter exit or quit. On OS/2, Windows NT, or Compaq OpenVMS Alpha use Ctrl-z. On UNIX systems, use Ctrl-d. Alternatively, on V5.3 of WebSphere MQ for AIX, Compaq Tru64 UNIX, HP-UX, OS/2 Warp, Solaris, and Windows, use the end command.

Displaying a channel

Use the MQSC command DISPLAY CHANNEL, specifying the channel name, the channel type (optional), and the attributes you want to see, or specifying that all attributes are to be displayed. In WebSphere MQ for AIX, iSeries, HP-UX, Linux, Solaris, and Windows systems, and MQSeries V5.1 for Compaq Tru64 UNIX, and OS/2 Warp the ALL parameter of the DISPLAY CHANNEL command is assumed by default if no specific attributes are requested and the channel name specified is not generic.

The attributes are described in Chapter 6, Channel attributes.

Display channel examples

DISPLAY CHANNEL(QM1.TO.QM2) TRPTYPE,CONVERT
 
DISPLAY CHANNEL(QM1.TO.*) TRPTYPE,CONVERT
 
DISPLAY CHANNEL(*) TRPTYPE,CONVERT
 
DISPLAY CHANNEL(QM1.TO.QMR34) ALL

Displaying channel status

Use the MQSC command DISPLAY CHSTATUS, specifying the channel name and whether you want the current status of channels or the status of saved information.

Display channel status examples

DISPLAY CHSTATUS(*) CURRENT
 
DISPLAY CHSTATUS(QM1.TO.*) SAVED

Note that the saved status does not apply until at least one batch of messages has been transmitted on the channel. In WebSphere MQ for AIX, iSeries, HP-UX, Linux, Solaris, and Windows systems, and MQSeries V5.1 for Compaq Tru64 UNIX, and OS/2 Warp status is also saved when a channel is stopped (using the STOP CHL command) and when the queue manager is ended.

Starting a channel

For applications to be able to exchange messages you must start a listener program for inbound connections (or, in the case of UNIX systems, create a listener attachment). In OS/2, Windows systems, and Compaq NonStop Kernel, use the runmqlsr command to start the WebSphere MQ listener process. Any inbound requests for channel attachment start MCAs as threads of this listener process. In Compaq OpenVMS Alpha, each receiver or server channel requires a listener process that then starts a channel process.

runmqlsr -t tcp -m QM2

For outbound connections you must start the channel in one of the following three ways:

Use the MQSC command START CHANNEL, specifying the channel name, to start the channel as a process or a thread, depending on the MCATYPE parameter. (If channels are started as threads, they are threads of a channel initiator.)
```
START CHANNEL(QM1.TO.QM2)
```
Use the control command runmqchl to start the channel as a process.
```
runmqchl -c QM1.TO.QM2 -m QM1
```
Use the channel initiator to trigger the channel.

Renaming a channel

To rename a message channel, use MQSC to carry out the following steps:

Use STOP CHANNEL to stop the channel.
Use DEFINE CHANNEL to create a duplicate channel definition with the new name.
Use DISPLAY CHANNEL to check that it has been created correctly.
Use DELETE CHANNEL to delete the original channel definition.

If you decide to rename a message channel, remember that a channel has two channel definitions, one at each end. Make sure you rename the channel at both ends at the same time.