The Fast communications manager (FCM) provides communications support for DB2 server products. Each database partition server has one FCM sender, and one FCM receiver daemon to provide communications between database partition servers to handle agent requests and to deliver message buffers.
The FCM daemon is started when you start the instance.
If communications fail between database partition servers or if they re-establish communications, the FCM daemons updates information (that you can query with the database system monitor) and cause the appropriate action (such as the rollback of an affected transaction) to be performed. You can use the database system monitor to help you set the FCM configuration parameters.
You can specify the number of FCM message buffers with the fcm_num_buffers database manager configuration parameter and the number of FCM channels with the fcm_num_channels database manager configuration parameter. The fcm_num_buffers and fcm_num_channels database manager configuration parameter are set to AUTOMATIC as the default value. FCM monitors resource usage when any of these parameter are set to automatic, and incrementally releases resources. It is recommended to leave these parameters set to AUTOMATIC.