This subsection describes the session ID format used for identifying the session information. The HttpSession object is identified by the session ID.

The session ID format depends on whether the following functionality is used:

• Redirector-based load balancing functionality
• Functionality to append a server ID to the session ID

The session ID is guaranteed to be unique in the J2EE server. However, if you want to set a unique value across multiple J2EE servers, add a worker name or server ID to the session ID and ensure that the worker name or server ID is unique across multiple J2EE servers.

The following figure shows the session ID formats for the used functionality:

Figure 2-11 Session ID format

Each case is described below.

• When both the redirector-based load balancing functionality and the server ID addition functionality are not used
  The session ID is 32 alphanumeric characters. These alphanumeric characters form a unique value on a J2EE server.
  
• When the redirector-based load balancing functionality is used
  The session ID consists of 32 alphanumeric characters, period (.), and worker name. You must specify a unique name for each server with the worker name.
  For details on the redirector-based load balancing functionality, see the description related to the use of the load balancer in 4.2 Distributing requests with the Web server (Redirector).
  
• When the server ID addition functionality is used (When the redirector-based load balancing functionality is not used)
  The session ID consists of 32 alphanumeric characters and the server ID. You must specify a unique value for each server with the server ID.
  For details on the server ID addition functionality, see 2.7.6 Adding a server ID to the session ID and Cookie.
  Note that when you use the redirector-based load balancing functionality, the server ID is not added.
  
• When the database session failover functionality is used (when completeness guarantee mode is disabled) or when the EADs session failover functionality is used
  A session ID is formed of 32 alphanumeric characters, a server ID and 16 alphanumeric characters. The addition of a server ID to the session ID, by Server ID addition functionality is a prerequisite for using the database session failover functionality (when completeness guarantee mode is disabled) and EADs session failover functionality.
  Note that you must set a unique value for each server, in the server ID.
  For details on the Server ID addition functionality, see 2.7.6 Adding a server ID to the session ID and Cookie.
  For details on the settings that are the prerequisites for the database session failover functionality and EADs session failover functionality, see 5.4.2 Prerequisite settings in the uCosminexus Application Server Expansion Guide.