This parameter specifies the number of FCM channels for each database partition.
Fast communication manager (FCM) buffers are used for both inter-member and intra-member communications by default. To enable non-clustered database systems to use the FCM subsystem and the fcm_num_channels parameter, you had to set the intra_parallel parameter to YES
An FCM channel represents a logical communication end point between EDUs running in the DB2® engine. Both control flows (request and reply) and data flows (table queue data) rely on channels to transfer data between partitions.
When set to AUTOMATIC, FCM monitors channel usage, incrementally allocating and releasing resources as requirements change.
If you want to set the fcm_num_channels parameter to a specific value with the AUTOMATIC attribute and you do not want the system controller thread to adjust resources lower than the specified value, you need to configure the DB2_FCM_SETTINGS registry variable. To enable this behavior, set the FCM_CFG_BASE_AS_FLOOR option of the DB2_FCM_SETTINGS registry variable to YES (or TRUE). The DB2_FCM_SETTINGS registry variable value is adjusted dynamically.