IBM BPM, V8.0.1, All platforms > Tuning > Tuning parameters
MDB throttle
On WebSphere Application Server for z/OS , you can use the message-driven bean (MDB) throttle to control MDB processing. The MDB throttle prevents the z/OS WLM work queue from becoming full of messages while it is waiting to be processed by worker threads in the WebSphere Application Server servant.
The MDB throttle limits how far a message listener port reads ahead down a JMS queue (or topic). The MDB throttle ensures that the backlog of messages to be processed on the WLM request queue does not become too large.
The high and low thresholds for the MDB throttle are determined by the value of the maximum sessions parameter of the listener port. The high threshold is set to the maximum sessions value for the listener port. When this number of messages is queued up on the WLM work request queue, no further requests are queued until the number of concurrent requests drops to the low threshold, which by default is 50% of the maximum sessions value.
To avoid the situation in which there are idle threads in the WebSphere Application Server servant while the MDB throttle is blocking further requests from being queued, consider setting the maximum sessions value to twice the number of worker threads in the servant.
To set the maximum sessions value, open the administrative console and navigate to Servers > Server Types > WebSphere application servers > server_name > Messaging > Message listener service > Listener Ports > listener_port_name.