SAP Dispatcher: Structure, Functions, and Caveats

Architecture and Functions

Think of the SAP dispatcher as the gatekeeper of a gated community. He makes sure that authorized personnel enter and directs them to the appropriate place. The SAP dispatcher lies between the Internet and your SAP system. It is the entry point for HTTP(s) requests into your system, which consists of one or more NetWeaver application servers. The SAP dispatcher can accept or reject connections. When it accepts a connection, it balances the load to ensure an even distribution across the servers. The SAP dispatcher plays a vital role in security and also balances the load in your SAP system to maximize efficiency. You can use the SAP dispatcher in ABAP/Java systems and in pure Java systems, as well as in pure ABAP systems.

Structure of the SAP Dispatcher

The architecture is the same as the architecture of the Internet Communication Manager (ICM). The SAP dispatcher uses the same HTTP paradigm and is likewise structured in modules from sub handlers. But unlike the ICM, the SAP dispatcher does not directly pass incoming requests to a work process (such as a server process). Instead, it sends them to the ICM of the application server. The response of the application server to a request returns to the client using the same network connection via the dispatcher. If the application server, acting as the client, opens connections to external HTTP servers, these connections go direct to the server (or possibly via a configured proxy) and not via the SAP dispatcher. The SAP dispatcher has the function of a “reverse proxy,” rather than that of a “proxy.”

Directing HTTP Requests

Like the ICM, the SAP dispatcher uses a number of handlers to process incoming requests. With the exception of the ABAP handler and the Java handler, the handlers are called in the exact same sequence as conventional processing of HTTP requests. The dispatching handler comes last and enacts the load balancing, then forwards the request to the ICM of the appropriate application server.

Functions

The SAP Web dispatcher performs the following tasks:

· Selects appropriate application server (persistence with stateful applications, load balancing, ABAP or Java server).

· Filters URLs. You can define URLs that you want to be rejected, and by doing so restrict access to your system.

· Acts as Web cache. You can use the SAP dispatcher as a Web Cache to improve the response times and to conserve the application server cache.

· Manipulates requests. Depending on the SSL configuration, you can forward, terminate, and (re)encrypt requests.

Caveats

The SAP dispatcher is only useful in the Web environment. In the classic SAP system, load is balanced by the message server. Also, the SAP dispatcher forwards incoming HTTP requests to the application servers and returns the responses from the back end to the client. Outgoing requests (such as requests to a different SAP Web Application Server) are not sent via the SAP dispatcher. They are sent via the proxy server for the appropriate intranet.

Recommendations

It’s a good idea to use the SAP dispatcher when you use an SAP system with several SAP NW AS instances for Web applications. The SAP dispatcher is a program that you can run on the machine that is connected directly to the Internet. And, it is easy to get it set up. It requires minimal configuration; you just have to enter some simple parameters into the profile. The SAP dispatcher is helpful whether you want to cover one or both aspects of its functionality. If your main interest is in security functions, SAP dispatcher is your answer. If it is in load balancing, SAP dispatcher is your answer too. You get both benefits in one application.

Like any good gatekeeper, the SAP dispatcher gets to know the neighborhood and maintains everyone’s safety while keeping things running smoothly. At 1st Basis, we can make sure your SAP dispatcher conforms to your actual needs. Get the gatekeeper. Contact us today.

Here Are 12 SAP Monitoring Best Practices

You have invested in having the highest quality system, integrating inventory, finance, human resources, logistics, and everything else by implementing SAP. Now, to get the most of that system, it is crucial that it is functioning at its optimal level. In order to make sure that it is doing so, there are a number of monitoring options available to you. In this post, we will examine the best practices around SAP monitoring.

Why Is Monitoring Important?

SAP monitoring is important because the complexity of the system and the multiple users create numerous opportunities for something to go wrong. Usually, those errors would simply slow down the system and it would keep performing, though less effectively (think about the difference between high speed broadband internet and a dial-up modem). So, one significant benefit to SAP monitoring is to ensure peak efficiency. As you know, SAP coordinates all aspects of your business, including finances and accounting, customer and inventory databases. There is a lot of sensitive data there, and it is crucial that it is properly protected. Security concerns mean that SAP monitoring cannot be bypassed. Moreover, constant monitoring prevents issues from occurring in the same way your annual physical exam is intended to catch developing problem. You might discover that you have high cholesterol and therefore change your habits, now, to prevent coronary heart disease developing later. This element of proactive intervention is not often thought about, but it is an essential facet of SAP monitoring.

What Does it Monitor?

SAP monitoring can be divided into three different areas: critical tasks, SAP systems, and databases. The monitoring frequency differs among them; some things are checked every few seconds, some, every 24 hours. The monitoring system as a whole needs daily attention. Let’s look at these three areas in more detail.

Critical Tasks

There are really only 2 critical tasks. You need to check that the R/3 System is available to users and check that the daily backup has been executed without errors.

SAP Systems

There are a number of SAP systems that should be part of your daily monitoring routine:

· Make sure that all application servers are up and running.

· Check on work processes. (Note which are marked “running” or “waiting.”)

· Look at the Global Work Process overview. (None should be greater than 1800 per second.)

· Check for failed updates. (They may be marked as “update terminated.”)

· Check system log for errors, warnings, security messages, database problems. Investigate and rectify each.

· Review for canceled jobs.

· Check for old locks.

o When a user is accessing a particular object, it is “locked” so another user cannot change it simultaneously.

o Often these locks aren’t removed, and bottleneck the system as locked tables cannot be updated by other processes.

· Note the users on the system. Review for unknown or different user ID and/or terminal. **This should be done several times a day for best security.**

· Check for spool problems. If something shows “in process” for over an hour, it needs to be investigated.

· Check the job log for new or incorrect jobs.

· Review and resolve dumps. If there are excessive numbers of them or unusual dumps, pursue an inquiry.

· Look at buffer statistics. See if there are swaps.

Databases

Your databases are the foundations of your business. Keeping them secure, accurate, and accessible is key. SAP monitoring best practices call for a daily review of the error log to discover and deal with any problems. Another important monitoring tool is to check database growth. If tablespace is used more than 90%, add a new data file to it. If there are missing indexes, rebuild. Finally, carefully examine the database statistics log.

These SAP monitoring best practices will keep your business running efficiently and securely. You can be confident that future problems are being anticipated and ameliorated, too. SAP monitoring is a key service that 1st Basis offers. Our experts will undertake this daily task and customize it to suit your particular needs. Contact us now to get the most out of your SAP System.