This parameter indicates the maximum number of client connections allowed per member.
A setting of -1 means that the value associated with max_coordagents will be used, not the automatic setting or behavior. AUTOMATIC means that the database manager picks the value for this parameter using whatever technique works best. AUTOMATIC is an ON/OFF switch in the configuration file and is independent of the value, hence both -1 and AUTOMATIC can be the default setting.
For details, see: Restrictions and behavior when configuring max_coordagents and max_connections.
The Concentrator is OFF when max_connections is equal to or less than max_coordagents. The Concentrator is ON when max_connections is greater than max_coordagents.
This parameter controls the maximum number of client applications that can be connected to a member in the instance. Typically, each application is assigned a coordinator agent. The agent facilitates the operations between the application and the database. When the default value for this parameter is used, the Concentrator feature is not activated. As a result, each agent operates within its own private memory and shares database manager and database global resources, such as the buffer pool, with other agents. When the parameter is set to a value greater than the default, the Concentrator feature is activated.