1. Deployment Planning Guide
  2. About the Siebel Connection Broker

About the Siebel Connection Broker

The Siebel Connection Broker (SCBroker) server component provides intraserver load balancing. SCBroker distributes server requests across multiple Application Object Manager processes running on a Siebel Server.

SCBroker listens on a configurable, static port for new requests. When a new request is received, it forwards the request to the Application Object Manager process with the least number of running tasks, or forwards the request to another Application Object Manager process in round-robin fashion. A user session is created on this Application Object Manager. Thereafter, the requests that apply to this session are directly sent to the Application Object Manager process hosting the session.

SCBroker is enabled by default and has several parameters:

  • PortNumber. Sets the port number on which SCBroker listens. The default is 2321, but you can change the port number.

  • DfltTasks. Sets the default number of processes for SCBroker. The recommended value is 2.

  • MaxTasks. Sets the maximum number of processes for SCBroker. The recommended value is 2. This value cannot be less than DfltTasks.

  • AutoRestart. Default is On. If SCBroker terminates abnormally, then this setting allows it to restart automatically. Setting this parameter to Off or False is not recommended.

  • ConnForwardAlgorithm. The connection forwarding algorithm is the routing scheme for SCBroker to use when routing intraserver requests to Application Object Manager processes. Possible values are LL (least-loaded) and RR (round-robin). SCBroker uses the least-loaded algorithm by default.

    • LL. The least-loaded algorithm (default behavior) balances incoming Application Object Manager login requests. It identifies which Application Object Manager process is handling the least number of tasks and assigns that process to handle the session. If SCBroker determines that an Application Object Manager process is not responding to a request, then it sends subsequent requests to the next available Application Object Manager process (using least-loaded algortihm).

    • RR. The round-robin algorithm distributes all of the Application Object Manager login requests to the next Application Object Manager process in a round-robin fashion, that is, equal loads distributed in order and without priority. If SCBroker determines that an Application Object Manager process is not responding to a request, then it sends subsequent requests to the next available Application Object Manager process (using round-robin algortihm).

    For more information about the ConnForwardAlgorithm parameter, see the information that follows this list of parameters.

  • ConnForwardTimeout. The connection forward time-out determines how long SCBroker waits for an Application Object Manager process to accept a request. The default is 500 milliseconds. This time-out minimizes wait time when SCBroker forwards a connection request to an Application Object Manager process and the request cannot be accepted. If a time-out occurs, then SCBroker reports an error back to the Siebel Application Interface.

  • ConnRequestTimeout. The connection request time-out determines how long SCBroker waits for all of the packets in an incoming new request. The default is 500 milliseconds. This time-out minimizes SCBroker wait time when TCP/IP requests are incomplete. If a time-out occurs, then the request is sent back to the Siebel Application Interface.

More Information about the ConnForwardAlgorithm Parameter

As noted, you can use the ConnForwardAlgorithm parameter to specify either least-loaded or round-robin routing. The round-robin routing scheme does not take into account the number of running tasks for each Application Object Manager process. It simply forwards each request to the next Application Object Manager process among the available processes. The least-loaded algorithm considers only the current number of tasks for each Application Object Manager process that is running.

The Siebel Gateway provides the connect string for the Siebel Application Interface to use for sending each request to an Application Object Manager process. If Siebel Gateway fails to provide a connect string, then Siebel Application Interface resends the request to the Siebel Gateway up to five times, with five seconds between each request.

In many circumstances, how an individual connection request is forwarded might be the same for either forwarding algorithm. The actual forwarding behavior depends on these factors:

  • The setting of the ConnForwardAlgorithm parameter for SCBroker.

  • The settings of the ConnForwardTimeout and ConnRequestTimeout parameters for SCBroker.

  • The current number of Application Object Manager processes.

  • The current number of tasks for the Application Object Manager component and for each Application Object Manager process.

  • Patterns of requests for new tasks and patterns of threads being freed up through logouts.

  • Application Object Manager parameter settings controlling the maximum number of tasks and the minimum and maximum number of Application Object Manager processes. The applicable parameters are:

    • Maximum Tasks (MaxTasks)

    • Minimum MT Servers (MinMTServers)

    • Maximum MT Servers (MaxMTServers)

    For information about calculating the settings for MaxTasks, MaxMTServers and MinMTServers, see Siebel Performance Tuning Guide.

Sometimes an individual connection request is not forwarded to an existing Application Object Manager process but instead causes a new Application Object Manager process to start. This can occur with either forwarding algorithm, when each existing Application Object Manager process has reached its theoretical maximum number of tasks, based on dividing the maximum number of tasks by the maximum number of Application Object Manager processes. A new process starts only if the maximum number of tasks and the maximum number of Application Object Manager processes have not yet been reached.

For more information about applicable parameters, see also Siebel System Administration Guide and Siebel Performance Tuning Guide.