SAP Web provides the greatest flexibility by separating technology infrastructure into solutions. SAP Web Application server is a natural progression of SAP Basis and supports all existing and future components of mySAP Business Suite and SAP R/3 Enterprise in addition to all J2EE-based applications. These applications can be customized or provided by a third party. SAP Web Application Server also has the underlying technology for SAP Enterprise Portal, SAP Business Information Warehouse, and SAP Exchange Infrastructure.
The Internet Communication Manager
The Internet Communication Manager ensures communication between the SAP system (SAP Web Application Server) with the outside world using the HTTP, HTTPS, and SMTP protocols. In the server role, it can process requests from the Internet that have URLs with the server/port combination that the ICM responds to. Independently of the URL, the ICM then calls the corresponding local handlers. You need the ICM if you want your SAP Web AS to communicate with the Internet using HTTP(S), SMTP, or NNTP.
The ICM is part of the SAP Web AS. The ICM is implemented as an independent process and is started and monitored by the dispatcher. You can use profile parameters to set whether the ICM should be started and how it should be configured The ICM process uses a pool of worker threads to parallel process the load. Besides the pool of worker threads, which process incoming requests, the following ICM components are also implemented as threads:
The ICM contains plug-ins for the protocol-dependent tasks. The Internet protocols HTTP and SMTP each have a plug-in. The plug-ins perform the following tasks:
• All protocol-specific tasks
• Input and output data handling, data manipulation
• Local handling in the ICM or forwarding to the work process
A Closer Look at the HTTP Plug-In
HTTP is the protocol used to make HTTP requests and HTTP responses over an IP network. The HTTP plug-in has all the built-in features to handle both an HTTP request and an HTTP response. A key element in the HTTP plug-in is that the URL and the port are used to access the local ICM handler. This eliminates the need to create a user context in the work process each time that an HTTP request is made from an application. The HTTP plug-in uses a chain-forwarding approach to processing an HTTP request. Each handler is capable of processing a request; however, if the handler is unavailable, the HTTP request is forwarded to the next available handler for processing. This increases performance.
Local handlers are referred to as subhandlers and are called in series depending on the handler's profile parameter. A profile parameter associates a handler with a URL prefix. Therefore, a request for a particular URL prefix is sent to the next available handler in the series that corresponds to the URL prefix. ICM has six handlers:
A Look at the Internet Server
The Internet server has a cache where HTTP objects are stored before those objects are forwarded to the client who requests the object. This is more efficient than retrieving the object from the disk each time a client requests it.
The Internet server requires one millisecond to process a request for an object that is already in cache. This means that 3000 requests can be processed every second if a 4 CPU computer is used as the server. The first time a client requests an object, the object is retrieved from the disk (or from its original source) and is stored in the ICM server cache. Once in the cache, the object is then sent to the client. Each object stored in the ICM server cache has an expiration time that is identified by the icm/HTTP/server_cache_<xx>/expiration parameter. The object remains in cache until it expires. A subsequent request for the object requires that the object be again retrieved from disk and placed into cache before it is sent to the client.
An Inside Look at the Web Dispatcher
The web dispatcher is a key component of integrating the Internet with SAP because the web dispatcher is the software switch between SAP and the Internet. As HTTP requests are received, the web dispatcher directs the request to one or multiple SAP Web application servers based on the capacity of the server. In this way, clients receive the fastest possible response. The web dispatcher is a software switch that runs on the proxy server or whatever server is directly connected to the Internet. The icm/server_port_<xx> parameter tells the web dispatcher the port that will receive client requests. The rdisp/mshost parameter identifies the SAP message server and the ms/http_port identifies the port that the SAP message server uses to receive requests. Both of these are used by the web dispatcher to process incoming HTTP(S) requests.
The number of requests the dispatcher sends to a SAP Web AS will depend on the capacity of the server, and capacity is linked to the number of configured dialog work processes. If the request is the second or subsequent request from an existing session (a session cookie for HTTP requests, and the client IP address for HTTPS requests), then the web dispatcher makes sure that the request is sent to the application that is processing the client's requests for that session.
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Sap Basis Tutorial
Sap: From Sap R/3 To Sap Netweaver
The Architecture Of The Sap Web Application Server
Sap Netweaver: An Overview
Using Sap Systems
Upgrading To Sap R/3 Enterprise: The First Step Into Sap Netweaver
The Change And Transport System
Development Options With Sap Solutions: Abap Engine
User Management And Security In Sap Environments
Web Application Server System Management
Performance And Troubleshooting With Sap Solutions
Sap For It Managers: Implementation, Planning, Operation, And Support Of Sap Systems
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