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Background documentationServer Groups in the Internet Communication Framework Locate this document in the navigation structure

 

In the ICF (Internet Communication Framework, transaction SICF) within the SAP NetWeaver Application Server, all virtual host names that can be handled by Application Server ABAP are configured (see also Virtual Hosts). Every virtual host name has a unique prefix with which the URL begins.

You can find some services in the HTTP service tree (transaction SICF) that provide information about URL prefixes and logon groups. These services can be found in the tree under sap/public/icf_info.

  • If you use HTTP Load Balancing Using the SAP Message Server, /urlprefix outputs the list of URL prefixes that are handled in the AS ABAP. This is how the message server finds out which URLs must be forwarded where.

  • /icr_urlprefix returns the same information, but for the SAP Web Dispatcher, if this is used for load balancing.

    Recommendation Recommendation

    Since there can be no redirects when the SAP Web Dispatcher is used, SAP recommends this method.

    End of the recommendation.

  • /logon_groups specifies a list of URL prefixes for which a logon group is defined (in transaction SICF). The requests are only forwarded to the server that is defined in this logon group. This is how a load distribution mechanism is implemented, based on URLs.

  • /icr_groups outputs all servers (host names) and logon groups that you have maintained in this system (transaction SMLG).

The SAP Web Dispatcher fetches this list from an application server. It can use this list to:

  • Decide whether it is an ABAP or a J2EE request

  • Carry out load balancing for the servers in question.

The procedure for this is described in detail in Server Selection and Load Balancing Using the SAP Web Dispatcher.

Relevant Profile Parameters

The following parameters are described in Parameters of the SAP Web Dispatcher.

  • is/HTTP/default_root_hdl determines which root directory should be used: the ICF (ABAP) root directory, or the root directory of the AS Java. Permitted values are abap and j2ee.

  • wdisp/max_server_groups specifies the maximum number of logon group entries that can be managed in the message server. The default is 128.

  • wdisp/max_server_group_name_len specifies the maximum length of a logon group entry.

  • wdisp/max_url_map_entries is the maximum length of the prefix entries that can be managed in the SAP Web dispatcher.

  • wdisp/max_url_map_path_len specifies the maximum path length of the URL mapping table of the SAP Web Dispatcher.

  • wdisp/group_info_location is the path in the HTTP service tree (transaction SICF), where information about the server groups for the SAP Web Dispatcher is stored.

  • wdisp/url_map_location The path in the HTTP service tree (transaction SICF), under which the URL mapping information for the SAP Web Dispatcher is stored.