Message metadata driver control

The message contains metadata structure. One of the elements of this structure is a character string known as "driver control," referred to as DRIVERCTL. This string can be used to insert protocol-specific information. For the WebSphere MQ protocol, this information consists of the MQMD values.

You can set any MQMD fields that are specified in this keyed list. Similarly, modify this keyed list to contain the MQMD values each time a message is read. This facilitates the getting of MQMD message values by Tcl. msgmetaset (a Tcl extension) is the command used to change the msg_driver_control string. The DRIVERCTL key value is used with this command to indicate that msg_driver_control is to be changed.