Editing the Instance Configuration File

The first time you run a broker, an instance configuration file is created containing configuration properties for that particular broker instance. The instance configuration file is named config.properties and is stored in a directory identified by the name of the broker instance to which it belongs:

…/instances/ instanceName/props/config.properties

(See Appendix A, Platform-Specific Locations of Message Queue^TM Data for the location of the instances directory.) If the file does not yet exist, you must use the -name option when starting the broker (see Broker Utility), to specify an instance name that Message Queue can use to create the file.

The instances/instanceName directory and the instance configuration file are owned by the user who created the corresponding broker instance. The broker instance must always be restarted by that same user.

The instance configuration file is maintained by the broker instance and is modified when you make configuration changes using Message Queue administration utilities. You can also edit an instance configuration file by hand to customize the broker’s behavior and resource use. To do so, you must be the owner of the instances/ instanceName directory or log in as root to change the directory’s access privileges.

The broker reads its instance configuration file only at startup. To make permanent changes to the broker’s configuration, you must shut down the broker, edit the file, and then restart the broker. Property definitions in the file (or any configuration file) use the following syntax:

propertyName=value [[,value1] …]

For example, the following entry specifies that the broker will hold up to 50,000 messages in memory and persistent storage before rejecting additional messages:

imq.system.max_count=50000

The following entry specifies that a new log file will be created every day (86,400 seconds):

imq.log.file.rolloversecs=86400

See Broker Services and Chapter 14, Broker Properties Reference for information on the available broker configuration properties and their default values.