Architecture of the SAP NetWeaver Application Server

Transcription

1 Architecture of the NetWeaver Application Release 7.1

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3 Online Help Content Architecture of the NetWeaver Application SCS Instance... 4 Start Service... 4 AS Only...4 AS Only... 5 Dual-Stack: Web Dispatcher... 7 High Availability with the Standalone... 7 Architecture of the NetWeaver Application

4 Online Help Architecture of the NetWeaver Application 7.1 An system consists of several application server instances, as well as one or more databases. SCS Instance In addition to multiple dialog instances that execute user requests, there is a special instance that contains the message server and the enqueue server - the SCS (System Central Services) for the AS, the ASCS ( System Central Services) for the AS. It is used for lock administration, message exchange, and load balancing in the system. It cannot process any dialog requests. : The enqueue server is another critical part of the transaction concept. It manages locks on database entries while they are being used by business programs. The lock concept works independently from transactions offered by the database management system. Traditionally, this functionality was offered by a specialized work process of the central instance. As of NetWeaver 7.1 a standalone enqueue server in a separate Central Services instance is used, which offers a more flexible system layout. Since there must be exactly one enqueue server per system, installing enqueue as part of the central instance or standalone enqueue in a Central Services instance (both depicted in figure 1) are mutually exclusive. The same applies for the message server. Message : The message server enables communication between the instances of a system. It also keeps track of the instances that are running in a system and the logon groups that each instance belongs to. It can balance the load between the instances of a system by redirecting logon requests (for, RFC or HTTP requests). It also provides the corresponding information to other load balancing components, like the Web Dispatcher. Start Service As implied by the name, this service starts the entire instance. Every instance has a start service although it is left out in some instances in figure one for simplicity. It also provides monitoring information about the instance state. On Windows it is implemented as a service that starts with the system. It is also integrated with the Windows Management Console and offers a servlet which provide the user with a console to operate the instance manually. In addition, all functions can be used non-interactively via a Web service interface. You have the following installation options for the application server platform: AS Only The following graphic depicts an -only system with one dialog instance and the Central Services (SCS) instance. Architecture of the NetWeaver Application

5 Online Help R R Internet Communication Manager (ICM) () Dispatcher Start Service Gateway start Message Database schema AS Central Services The Application consists of the following major components: The dispatcher handles communication with clients using the DIAG protocol. It is also the central controller of an instance. It prepares shared memory data structures, starts and controls the other processes and dispatches requests to the work processes (also requests handled by Gateway or ICM). If all the processes are occupied, the requests are stored in the dispatcher queue. The work processes execute programs. A work process is controlled by the taskhandler and contains the to execute programs. The Gateway provides the RFC interface between the instances (within an system and beyond system boundaries). Both client and server functionality are supported. AS Only The following graphic depicts a -only system (e.g. a CE system) with one dialog instance and the Central Services instance. The AS components include: The Internet Communication Manager handles incoming requests (HTTP(S), IIOP, P4, telnet) and forwards them to the appropriate server process. The server processes execute requests. The instance controller controls and monitors the life cycle of the AS instance. Architecture of the NetWeaver Application

6 Online Help Client HTTP(S), IIOP P4, telnet Internet Communication Manager (ICM) start Message Central Services SP SP SP SP SP SP Start Service Instance Controller Database schema AS Dual-Stack: + The following graphic depicts a dual-stack system with one dialog instance and the Central Services instance. R R Internet Communication Manager (ICM) () Dispatcher Database schema Start Service Gateway AS JCo start Message Central Services SP SP SP SP SP SP Start Service Instance Controller Database schema AS A dialog instance with AS and AS share the following components: Architecture of the NetWeaver Application

7 Online Help The Internet Communication Manager (ICM) sets up the connection to the Internet. It can process both server and client Web requests. It supports HTTP, HTTPS und SMTP protocols for the AS. In AS the ICM supports the HTTP(S), P4, IIOP and Telnet protocols. The NW AS can act as a Web server or a Web client. Central services (message server and enqueue server) The different stacks can share the database, but they need different DB schemas. More information: Library - Architecture of the NetWeaver Application Web Dispatcher For Web requests it is usually desirable to handle all requests to a system with one Web server address. The Web dispatcher serves as single point of entry to the system for HTTP(S) requests. It dispatches request between the instances of the system based on information retrieved by the Message. The Web Dispatcher is a standalone program which is ideally located in the network s DMZ. Load Balancing and Configuration: Information from Message Message Enq. Serv. Central Services Client Web Dispatcher NW AS (DI) NW AS (DI) RDBMS Single Access Point: an IP Address, Port and URL DMZ (Demilitarized Zone) NW AS (DI) Intranet More information: Web Dispatcher High Availability with the Standalone The enqueue function is not just available in the classical central instance, it is also available in a standalone server that is not part of AS. The standalone enqueue server is used in the following scenarios: AS provides a locking service based on the enqueue function. The standalone enqueue server, which forms the SCS Instance together with the message server, is used for this. You can use the standalone enqueue server as part of a high availability (HA) solution. Architecture of the NetWeaver Application

8 Online Help The HA enqueue server consists of the standalone enqueue server and an enqueue replication server. The replication enqueue server runs on another host and contains a replica of the lock table (replication table). The following graphic shows the HA configured within the SCS of an system. The high availability configuration with enqueue replication server is independent of the system type. Dispatcher Dispatcher Client Client Lock Table Host A HA Software Replication Replication Table Host B High Availability The message server, which is also part of the SCS, has no critical data like the lock table and can simply be restarted in case the server crashes. This is also done by the HA software. More information: Standalone in the Technical Operations Manual Architecture of the NetWeaver Application