WebSphere® MQ message queue access

You can access only one connecting queue manager at a time; however, you can access multiple queues that are under the control of the connecting queue manager. If you wish to connect directly to a queue manager other than the current connecting queue manager, you must disconnect from the first queue manager by invoking MQDISC, then connect to the second queue manager by invoking add, get next, MQCONN, or MQCONNX.

You can also access queues that are under the control of a remote queue manager, which is a queue manager with which the connecting queue manager can interact. Access between the two queue managers is possible only if WebSphere® MQ itself is configured to allow for that access.

Access to the connecting queue manager is terminated when you invoke MQDISC or when your code ends.

When queue-access statements are not in a unit of work, each change to a message queue is committed immediately.

When your code ends a unit of work, EGL commits or rolls back all recoverable resources that are accessed by your program, including databases, message queues, and recoverable files. This outcome occurs whether you use the system functions (sysLib.commit, sysLib.rollback) or the EGL calls to WebSphere® MQ (MQCMIT, MQBACK); the appropriate EGL system function is invoked in either case.

A rollback occurs if an EGL program terminates early because of an error.

You can customize your interaction with WebSphere® MQ rather than relying on the default processing of add and get next statements.

You must carry out the following tasks:

1. Import the files into an EGL project from the following directory:

   sharedInstallationDir\plugins\
   com.ibm.etools.egl.resources_version\MqReusableParts

   sharedInstallationDir

   The shared product installation directory, such as C:\Program Files\IBM\SDP70Shared. If you installed and kept a Rational® Developer product before installing the product that you are using now, you might need to specify the directory from the earlier installation.

   version

   The latest version of the plugin; for example, "7.0.100.RFB_20080711_1614".

2. To make the parts more easily available to your program, write one or more EGL import statements in the file that contains your program. If the files to be imported reside in a project other than the one in which you are developing code, make sure that your project references the other project.

   For details, see Import and use statements.

3. In your program, declare global variables:
   • Include use declarations for the mqrc, mqrcode, and mqvalue DataTables.
   • For each options record that you wish to pass to WebSphere® MQ, declare a basic record that uses an options record part as a typedef. For details on each part, see Options records for MQRecords.
4. In your function, initialize the options records that you intend to pass to WebSphere® MQ by invoking the imported EGL initialization function for each record. Each function has the name of a Record part followed by _INIT, for example, MQGMO_INIT.
5. Set values for the fields in the options records. The mqvalue DataTable contains a single row of fields, each of which corresponds to a symbol that is described in the WebSphere® MQ documentation. You can set a value for a field in an option record by using one of the fields in the mqvalue DataTable, as in the following example:

   mqgmo.options = mqvalue.mqgmo_lock[1];

   You can set a numeric field in an option record to a combination of values by adding the values, as in the following example:

     mqgmo.options = mqvalue.mqgmo_lock[1] 
                     + mqvalue.mqgmo_accept_truncated_msg[1] 
                     + mqvalue.mqgmo_browse_first[1];
   

6. The details of when you need to generate tables depend on whether your target program language is COBOL or Java™. To generate all the data tables that are used in your program, allow the build descriptor option genTables to default to YES. For more information, see DataTable part.