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Basics of SAP BASIS !!! Part 1 – Intro to ABAP Web Application Server

As a SAP Basis Administrator I know that a lot of non-technical and new SAP Consultants initially find it difficult to Understand to ABAP Application Server.

This is a quick Overview of SAP Application Server for SAP functional consultants, Developers and non-basis technical consultants who want to understand how SAP Applications actually run in a ABAP system. And also for others who wants to understand SAP BASIS and get a head start.

 

To understand BASIS lets start with the basics. Lets understand the first layer  in SAP Netweaver called the ‘Web Application server’. Well don’t be afraid, I will keep it as simple as I can without getting into jargons or terminology.

 

Have you ever wondered what goes behind the SAP screen when you click a button to see a report?

– It is very interesting, let’s start with what you see on the screen, the GUI , it is called SAP GUI.

 

  • SAP GUI installed on your local PC, displays the screen according to the ABAP program that you are running. 

 

How dose SAP GUI come to know what is to be displayed and what data it needs to fetch and where it is to be stored?

– All this is taken care by the ABAP program that is executed on the Application Server

 

What comprises of this SAP application server?  

– Well there are many components but lets discuss the bare minimum to keep it simple. SAP GUI communicates with Application server that has a DISPATCHER and 5 different processes to execute the ABAP program.  These 5 different processes are called WORK PROCESS in SAP, as they do all the hard work.

 

 

Lets look at the  different work process and the work they do.

 

  • Any program that needs a screen to be displayed to the user (i.e. requires data inputs from the users) is executed by DIALOAG work process. It will fetch the needed ABAP program and execute it for you. There may be two or more of this kind depending on the load on the server.

 

  •  Any kind of printing job is taken care by SPOOL work process.  When you press the print button, this process will to the needful to get the printout.

 

  • Any kind of job that just need data to be processed and can be done without user intervention is executed my BACKGROUND work process. All batch processing jobs are background jobs.

 

Now lets see the work processes that are required to keep the DATA consistent.

 

  • The ENQUEUE process ensures that data that one user is editing cannot be changed by other user. It is a kind of Lock mechanism.

 

  • The UPDATE work process writes the data that you have entered in your screen to that Database once you have completed your full transaction. There are two of them.

So this sums up 5 different work process and the work they do.

 

 

 

Now lets see process that handles the communication part of the Application Server.

 

We need a coordinator among different work processes, a kind of team Lead to say who will do which work and when.

  • For this we have a DISPATCHER, it organizes the communication between the work processes and also between the SAPGUI.

 

We need a process that keeps info about all processes and help the dispatcher to balance the load among them.

  • Message server dose exactly that. It also helps to established initial connection between SAP GUI and application server when the user logs in for first time and used for communication with other Systems in the landscape.

 

 

 There is a lot more to this Architecture but this is to give very geb=neral idea of what goes on in the WAS APAB.

I hope that the picture of the SAP Application server is now clear in your mind. Have a look at the image below –image

Let me summarize it for you. 

  • User interacts with the Application server using SAP GUI .
  • SAP message server establishes the initial connection between user and Dispatcher.
  • Dispatcher will decide which work process is to be called according to user interaction.
  •  Different work process (Dialog , spool, background, enqueue , update) do their job as define above.

 

Now you know about SAP GUI, Message Server, Dispatcher and 5 different work process. Next time when any basis guy comes and throws all this terms at you, you know what they exactly mean.

 

Note: The Architecture described above is an ABAP system. SAP JAVA Application sever has the message server and the dispatcher but dose not have work process . It has servers threads that will do the job of java program executions and stuff. I will cover that in other blog.

Other Reference :

SAP Web Application Server FAQ

Architecture of the SAP NetWeaver Application Server 

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      11 Comments
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      Author's profile photo Raja Thangamani
      Raja Thangamani
      Thanks for sharing the information. It will be useful if you can share how to apply the support pack and apply the enhancements steps.

      Regards
      Raja

      Author's profile photo Former Member
      Former Member
      Blog Post Author
      I am glad you found it helpful..
      I will surely cover different Basis technical Activities.
      I will try and keep it simple giving reference to material provided by SAP. So that everyone can understand the technical concept behind it.
      Author's profile photo Former Member
      Former Member
      here

      it makes more sense to keep it as the wiki, as it means others can add to it.

      Author's profile photo Former Member
      Former Member
      Blog Post Author
      Hi,

      Thanks for the feedback. Actually I want to keep it as a blog. cause I plan to write more about technical basics; in simple terms for all to understand.
      Wiki page can be attributed to pure technical people and will start getting more complex as people start adding more technical stuff. I want to keep it short and simple.
      I will remove that wiki page.

      Author's profile photo Former Member
      Former Member
      Very good post - thanks for sharing. I like the idea of a simplistic approach to help the beginners out. Perhaps a possible future post could be on upgrading the Kernel... Another topic that is very confusing in Basis is versions of components - which work together etc. For example, getting ECC6 installed on Win 2008 R2 - what version can you install? Maybe even an explination of the installation DVD's or SAPCAR files, and how they all fit together. Just some food for thought to help fuel upcoming posts 🙂

      Cheers,
      David

      Author's profile photo Hemanth Kumar
      Hemanth Kumar
      Hi David,

      Below links will be helpful for kernel upgrade:

      http://www.sdn.sap.com/irj/scn/index?rid=/library/uuid/
      70d8838d-cb8f-2c10-7ab8-d1504670fbb8
      and
      Video Blog: Applying Support Packages Stacks with JSPM

      Regards,
      Hemanth
      SAP AGS

      Author's profile photo Former Member
      Former Member
      Thanks Hemanth,

      I'll check those links out

      Regards,
      David

      Author's profile photo Former Member
      Former Member
      Blog Post Author
      hi,

      Thanks for the encouragement. I will surely cover regular Basis Activities such as kernel upgrade, SAP GUI Upgrade, Support Pack upgrade.
      I will surely not include step to step procedure. Cause its available in SAP Documentation. But I will try and present the concept in simple manner so that actual procedure makes sense.

      Author's profile photo Former Member
      Former Member
      Blog Post Author
      hi,

      Thanks for the encouragement. I will surely cover regular Basis Activities such as kernel upgrade, SAP GUI Upgrade, Support Pack upgrade.
      I will surely not include step to step procedure. Cause its available in SAP Documentation. But I will try and present the concept in simple manner so that actual procedure makes sense.

      Author's profile photo Former Member
      Former Member
      Blog Post Author
      hi,

      Thanks for the encouragement. I will surely cover regular Basis Activities such as kernel upgrade, SAP GUI Upgrade, Support Pack upgrade.
      I will surely not include step to step procedure. Cause its available in SAP Documentation. But I will try and present the concept in simple manner so that actual procedure makes sense.

      Author's profile photo Nurhayati Rosli
      Nurhayati Rosli

      Hi ,

      I just surfed this page to learn about BASIS .. i really liked the way you explained it .

      I know its very late since 9 years now with this post , but still wanted to know if there is continuation of this parts 2,3,..

      Please do guide me in learning BASIS .

      Thanks ,

      Nizam