Configuring the agent's data channel

In some scenarios, it may be necessary to provide some buffering between the agent and the Agent Controller. Buffering is done by using a data channel between the agent and the Agent Controller. Data channels are desirable in situations where agent performance is highly important. Without a buffer, it is possible that the agent may become blocked when performing output as the test client may not be able to process the output as quickly as required.

The data channel is configured with the <Agent> element in the configuration file of the plug-in that contains the agent. For example, the data channel for the Java Profiling Agent is configured by changing its <Agent> element in plugins/org.eclipse.tptp.platform.collection.framework_<version>/config/pluginconfig.xml.

To modify the <Agent> element in the configuration file:

Locate the configuration file that contains the element to be modified. It will either be the serviceconfig.xml file or the pluginconfig.xml file for the plug-in that contains the agent. See the related task.
Open it in an editor, and search for the <Agent> element.
Modify the value of the dataChannelSize attribute.
For example,
To specify that a data channel of 64 megabytes is to be used when the Java Profiling Agent is actively profiling, change the value of the dataChannelSize attribute to 64 MB.
```
<Agent name="Java Profiling Agent" type="Profiler" 
  dataChannelSize="64MB"> 
</Agent>
```
On Linux, the maximum data channel size is limited by the maximum shared memory size of the system. This configuration setting is located in /proc/sys/kernel/shmmax. The data channel will fail to be created if the dataChannelSize attribute value is greater than that specified in the /proc/sys/kernel/shmmax.

On Solaris, the maximum data channel size is limited by the shared memory size of the system. The configuration setting is located in /etc/system under the shmmax attribute. The data channel will not be created if the dataChannelSize attribute value is greater than the shmmax attribute specified in the /etc/system. If that attribute does not exist, its value is assumed to be 1 MB, by default.

On HP-UX, the maximum data channel size is limited by the shared memory size of the system. The configuration setting is located in /etc/conf/master.d/core-hpux under the shmmax attribute. The data channel will not be created if the dataChannelSize attribute value is greater than the shmmax attribute specified in /etc/conf/master.d/core-hpux. If that file or attribute does not exist, its value is assumed to be 64 MB, by default.

On AIX, the maximum data channel size is limited by the maximum shared memory size of the system, which is fixed at 256 MB. The data channel will not be created if the dataChannelSize attribute value is greater than 256 MB.

On z/OS, the maximum data channel size is limited by the maximum shared memory segment size of the system. This configuration setting is located in the IPCSHMMPAGES parameter in the MVS BPXPRMxx parmlib member. The value of IPCSHMMPAGES should be set to the maximum number of 4K pages that a data channel can be. For example, if the dataChannelSize is to be set to 32M in serviceconfig.xml, then IPCSHMMPAGES must be set to a value greater than 8192. The data channel will fail to be created if the dataChannelSize attribute value is greater than 4K times the value of IPCSHMMPAGES.

To allow the Agent Controller to communicate with a large number of agents simultaneously, the IPCSHMNSEGS parameter in the MVS BPXPRMxx parmlib member must be set to an appropriate value. The IPCSHMNSEGS parameter specifies the maximum number of attached shared memory segments or data channels for each address space. The default value is 10. A value of 50 would enable 50 agents to communicate with the Agent Controller simultaneously.