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This article introduces the knowledge of "what are the components of the ABAP application server". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

A typical ABAP application server consists of the following components:

(1) Internet Communication Manager (ICM)

(2) ABAP dispatcher

(3) Task handler

(4) several working processes, such as dialog, update, print, background, etc.

(5) RFC Gateway

(6) Standalone enqueue server

(7) SAP Message Server

The relationship between these components is shown in the figure below. A SAP system can contain multiple application server instances, but only one ASCS instance.

The functions of each component are briefly described below.

Internet Communication Manager (ICM)-SAP NetWeaver

ICM is a separate process in the Netweaver server, which is started and monitored by ABAP Dispatcher, and is responsible for the network communication between the SAP system and the outside. Based on the parsing of the received request URL, the ICM distributes the request to the specific handler for processing.

The protocols commonly used by ICM to interact with Internet are HTTP,HTTPS,SMTP and so on.

The following figure is an architectural diagram of ICM.

Thread Control: this thread is responsible for receiving external requests, taking idle worker threads from the ICM thread pool, and handing over the context of the request to the worker thread.

Worker thread: responsible for the specific processing of requests, including an Imax O processor, which can be used for network input and output operations. For requests of different protocol types, Thread Control dispatches worker threads that contain the corresponding protocol plug-ins.

Watchdog: if a worker thread waits for a response until it times out while processing a task, Watchdog releases the worker thread to avoid waiting indefinitely, so that the worker thread can serve other requests. Watchdog, on the other hand, continues to wait for a response that has not yet arrived. Then, if the response arrives, Watchdog notifies Thread control, which will continue to call the new worker thread to process it.

Signal Handler: handles signals from the operating system or other processes.

Connection Info: this table maintains the status information for each connection, including memory pipes, etc.

Memory Pipes: a memory pipe is a memory-based communication data structure that is used to transfer data contained in external requests received by ICM to the worker thread.

Internet Server Cache: server-side cache that can speed up response to repeated requests.

ABAP Dispatcher and work process

The relationship between the two is clear in the following figure, where there are many different types of worker processes running on the ABAP application server.

SAP gateway

Communication is carried out between SAP systems and between SAP systems and external systems through TCP/IP-based RFC calls, while gateway serves as the entry point for RFC call distribution, as shown in the following figure:

SAP Message Server

Each SAP system can contain only one message server, which is responsible for the following tasks:

(1) as a communication channel between multiple application server instances in the SAP system

(2) load distribution of login requests from clients through SAPGUI and SAP RFC

When an application server instance is started, its dispatcher process contacts the message server to report to it the types of services it can provide.

SAP Router

A stand-alone program that protects the SAP system from unauthorized requests.

In the network connection topology, SAProuter plays the role of proxy between SAP systems and between SAP systems and external networks. It is a supplement to the firewall mechanism based on port filtering and is usually installed directly on the firewall host.

SAPRouter maintains a table of routing permissions to maintain what types of requests are allowed to connect to the SAP system behind the firewall.

SAP Start Service

The service runs on the server where the SAP application server instance is deployed, and the implementation carrier is the system service of windows (sapstartsrv.exe) and the Daemon process of Unix system (sapstartsrv).

The functions implemented by SAP Start Service are:

(1) start and terminate SAP application server instances and monitor their running status

(2) Reading and management of application server logs, tracking and configuration files

Enqueue Server

Implement lock management mechanism at the ABAP application level. The locks held by all users in the current session on the application server instance are maintained in the lock information management table of the Enqueue server, which is maintained in the memory of the Enqueue server and will not be persisted, so the Enqueue server has become one of the sources of single point of failure of the ABAP system: when the Enqueue server is running for various reasons, the data of the lock information table maintained in memory will be lost.

Therefore, in order to ensure the high availability of the Enqueue server, it is usually deployed on a separate physical host, or even multiple Enqueue servers with master-slave mechanism are introduced to synchronize the lock information management tables on the Master Enqueue server to other Enqueue servers.

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