Activation specifications

Message-driven bean applications, that are configured to use an activation specification, have conversations active for activation specification to monitor a JMS destination, and for every server session used to run a message-driven bean instance to process messages.

The following conversations are active for message-driven bean applications that are configured to use an activation specification:

  • One conversation for the activation specification to monitor a JMS destination for suitable messages. This conversation is starts as soon as the activation specification starts, and remains active until the activation specification stops.
  • One conversation for every server session used to run a message-driven bean instance to process messages.

The activation specification advanced property Maximum server sessions specifies the maximum number of server sessions that can be active at any one time for a given activation specification. This property has the default value of 10. Server sessions are created as they are needed, and are closed down if they have been idle for the period of time specified by the activation specification advanced property Server session pool timeout. The default value for this property is 300000 milliseconds (5 minutes).

Conversations start when a server session is created, and are stopped either when the activation specification is stopped or when a server session times out.

This means that the maximum number of conversations from a single activation specification to IBM MQ can be calculated using the following formula: 
Maximum number of conversations = Maximum server sessions + 1
The number of channel instances that are created to allow this number of conversations to take place can be found by sing the following calculation: 
Maximum number of channel instances =
    Maximum number of conversations / SHARECNV for the channel being used
Any remainder from this calculation can be rounded up. For a simple activation specification, that uses the default value for the Maximum server sessions property, the maximum number of conversations that can exist between WebSphere Application Server and IBM MQ for this activation specification is calculated as: 
Maximum number of conversations = Maximum server sessions + 1
For example: 
    = 10 + 1
    = 11
If this activation specification is connecting to IBM MQ using a channel that has the SHARECNV property set to 10, then the number of channel instances that are created is calculated as: 
Maximum number of channel instances =
    Maximum number of conversations / SHARECNV for the channel being used
For example: 
    = 11 / 10
    = 2 (rounded up to nearest connection)
Parent topic: Determining the number of TCP/IP connections that are created from WebSphere Application Server to IBM MQ