Server lists

The server list is used by IBM® Data Server drivers and clients for workload balancing (WLB) and automatic client reroute (ACR) operation. The server list contains a list of addresses and the relative priority of those addresses. When a client connects to a Db2® server over TCP/IP, the server list is returned to and cached by the client. The server periodically provides a refreshed server list to the client.

The default server list forms the basis for workload balancing (WLB) and automatic client reroute (ACR) operations by IBM Data Server drivers and clients. Periodically, the remote driver or client asks a member to return a server list for the database accessed. Each member stores its copy of a server list for a particular database in a cache.

Each entry in the server list contains:

Host list: a fully qualified host name
Port: indicates which Db2 server's TCP/IP communication manager is listening on
Priority: The value indicates what ratio of work is driven to this server in relation to the other servers in the server list. The member priority is a relative value that is meaningful only when compared with another member. The higher the priority, the more work the member can handle relative to members with lower priorities, and therefore it is given more work by the driver or client for that database. A priority of 0 means that the address is used only by the client as a last resort.

In a Db2 pureScale® instance, the default server list that is returned to the client contains an entry for each member where a TCP/IP communications manager is running, and the address for the cataloged alternate server (if there is one.) In a partitioned database environment, the default server list exists only if there is a cataloged alternate server. When there is a cataloged alternate server, the default server list contains the address of the member the application that is connected to and the address of the alternate server.