To change the number of threads that a message flow node
can use at run time to process messages, you can configure the Additional instances property of an Input node that is
included in a message flow or subflow added to a BAR file.
About this task
The following figure outlines the configuration properties
of a message flow node:

WebSphere® Message Broker allocates threads to a message flow as follows:
- By default, one thread is allocated per Input node. The Input
node can be defined in the main message flow or within a subflow.
- The default value of the Additional instances property is 0 threads. The maximum value of the Additional
instances property is 256 threads.
- All instances defined in the Additional instances property for an Input node are started by WebSphere Message Broker as required.
- The number of threads available to process messages when you start
a message flow is by default equal to the number of Input nodes plus
the number of additional instances configured for each Input node
in the BAR file manage section.
- If you have a subflow included in a message flow, you can configure
additional instances for each Input node modeled within the subflow.
This condition applies whether the subflow is used as the starting
node in a message flow, as a middle node in a message flow, or as
the last node in a message flow.
Procedure
To add more threads to process messages by a specific
Input node, you must complete the following steps:
- Open the BAR file that contains the message flow and subflows
for which you want to set the Additional instances property. In the Broker Development view, identify the project that contains the BAR file, and double-click
the file to open it.
- Set the Additional instances property
of the Input node that is included in the BAR file to a value greater
than 0 and up to 256.
Note: If you set the value to
a number greater than 256, the BAR file will fail to deploy.
- Change the Additional instances pool to Use Pool associated with Node.
Results
Based on your message flow design and configuration, the
following tables summarize the number of threads available when running
the message flow in WebSphere Message Broker:
Table 1. Sample summary table of parallel
threads available when running a message flow in a brokerNumber of Input nodes in a message flow or subflow |
Number of default instances or threads per message
flow (1 thread per input node in a message flow) |
Additional instances property (set at input
node level) |
Maximum number of threads that can process messages
in parallel |
1 |
1 |
0 |
(1+0) = 1 |
1 |
1 |
1 |
(1+1) = 2 |
1 |
1 |
2 |
(1+2) = 3 |
2 |
2 |
0 |
(1+0) + (1+0) = 2 |
2 |
2 |
Additional instances = 1 for all Input nodes |
(1+1) + (1+1) = 4 |
3 |
3 |
Additional instances = 2 for all Input nodes |
(1 +2) + (1 +2) + (1 +2) = 9 |
3 |
3 |
Additional instances = 1 for one Input node;
Additional instances = 2 for another Input node; Additional instances
= 3 for another Input node |
(1+1) + (1+2) + (1 + 3) = 9 |