max_connections - Maximum number of client connections configuration parameter

This parameter indicates the maximum number of client connections allowed per member.

Configuration type
Database manager
Parameter type
Configurable online
Applies to
  • Database server with local and remote clients
  • Database server with local clients
  • Database Server or Connect server with local and remote clients (for max_connections, max_coordagents, num_initagents, num_poolagents, and also federated_async, if you are using a Federated environment)
Default [range]
-1 and AUTOMATIC (max_coordagents) [-1 and AUTOMATIC, 1 - 64000]

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 on the restrictions and the behavior of interactions of max_connections and max_coordagents in a concentrator environment (including AUTOMATIC settings), see: Restrictions and behavior when configuring max_coordagents and max_connections.

The Concentrator

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.


The maximum number of client connections can be larger than the value set by the max_connections configuration parameter if the user holds one of the following authorities:
Note: Bypassing the maximum number of client connections set by the max_connections configuration parameter is useful for many reasons including the following tasks:
  • Administrative tasks
  • Capturing snapshot information
  • Critical troubleshooting tasks
  • Maintenance tasks (such as forcing users off the system)