SAP interfacing: RFC

SAP has many different ways to interface. The RFC (Remote Function Call) protocol is one of the most wide used.

This blog will explain best practices around secure and correct setup of custom built ABAP RFC function modules.

Questions that will be answered are:

  • How to setup RFC enabled function module?
  • How to setup proper RFC error handling?
  • How to setup security in RFC enabled function module?
  • How strict is the S_RFC authorization handling?
  • Why is SAP_ALL not sufficient for RFC handling?

Creation of test RFC enabled function module

In SE37 you can setup an RFC enabled function module just like a normal function module. First create a function group. Activate that function group in SE80. Now you can create the function module. We will call our test module ZBAPIDEMO:

Important here in the first tab is to set the processing type to Remote-Enabled Module.

For testing we setup import and export tabs:

Important here with RFC: set the Pass by value tickbox.

For tables use a suitable table type:

And setup the correct exceptions:

Here you can see 2 very important error messages that should always be implemented:

  1. An extra authorization check
  2. An error message when no data is found

Now we can implement the following simple source code:

   DATA: zls_coms_gen_textline TYPE coms_gen_textline.
 
   AUTHORITY-CHECK OBJECT 'S_CDMC'
   ID 'CDMC_AREA' FIELD 'A'
   ID 'CDMC_ROLE' FIELD 'U'.
   IF sy-subrc EQ 0.
 
     CASE zimport.
       WHEN 1.
         zexport = 'Hello world'.
       WHEN 2.
         zls_coms_gen_textline-entry = 'Hello world table 1'.
         APPEND zls_coms_gen_textline TO ztable.
         zls_coms_gen_textline-entry = 'Hello world table 2'.
         APPEND zls_coms_gen_textline TO ztable.
       WHEN OTHERS.
         RAISE not_found.
     ENDCASE.
 
   ELSE.
     RAISE not_authorized_business.
   ENDIF. 

What is important here in this source code:

  1. The authorization check is implemented and raises an error
  2. If no data is found the NOT_FOUND error is raised

With the SE37 test suite you can test diverse scenario’s now.

Calling RFC function module from another ABAP system

If you call this RFC function module form another ABAP sytem you have to make sure you have set and check the following exceptions:

  exceptions
      not_authorized_business = 1
      not_authorized          = 2
      system_failure          = 3
      communication_failure   = 4
      not_found               = 5
      OTHERS                  = 6.

There are 2 exceptions from the BAPI definition:

  1. NOT_FOUND (nothing found)
  2. NOT_AUTHORIZED_BUSINESS (our own implemented business authorization check)

4 exceptions should be implemented as part of the RFC framework:

  1. NOT_AUTHORIZED: this is the RFC authorization, which will be explained next chapter
  2. SYSTEM_FAILURE: the coding has caused a dump and the system returns and error message (see OSS note 2484377 – Error Message: “RFC Exception SYSTEM_FAILURE Raised; No More Memory Available to Extend an Internal Tab” Upon Executing a Data Extraction Run as an example)
  3. COMMUNICATION_FAILURE: the call to the other system fails. Most likely if you go to SM59 to the RFC destination and perform a connection test you will get a failure.
  4. OTHERS: something else went wrong

The developer should take proper care of these error situations.

Dear ABAP developers: the basis team member are also humans. They will make RFC configuration errors, they rely on the authorization team to assign the correct roles and they rely on infrastructure providers to make sure systems are up and running. Also the basis team will need to perform patching and upgrades to the system, which you as ABAP developer, are calling. So please don't blame the basis team for these exceptions, but please be a good developer and implement proper error handling. If you didn't implement proper error handling, and something went wrong on basis side, that caused your code to go wrong, think twice before putting blame on basis if your code is not handling the situation properly.

For reference: OSS note 1371131 – Correct error handling of RFC calls.

Security of RFC calls

Security of RFC calls is consisting of 2 layers:

  1. The RFC layer
  2. The business application code

You should always implement both layers!

The RFC layer is protected by authorization object S_RFC:

Here you can choose between a function group or even allowing per function module. Personally I would protect by function module. Background: create, change and display BAPI’s will normally be developed inside same function group.

There is a common misunderstanding that if you give SAP_ALL to a (background) user, this would solve the RFC authorization issues. This is not true. SAP_ALL does not contain the S_RFC rights. You have to hand them out separately.

Best practice 1: you might want to start with broad authorizations at the beginning of a development to rule out authorization issues. But you must definitely limit the rights before you make the development go productively live.

Best practice 2: as first statement inside each and every RFC function module, program a relevant business authorization check statement. This is an extra safety measure that is needed to protect important business data from authorization consultants that have handed out * authorizations in object S_RFC (* means all).

More on checking the basis RFC security: read this blog.

Generic S_RFC check handling at basis level

The behavior of the S_RFC check is driven by the settings of RZ11 profile parameter auth/rfc_authorithy_check. Please make sure it has a setting of 6 or higher. Best is 9. A system with 5 or lower can be considered as insecure!

Background OSS note: 2216306 – S_RFC check and profile parameter auth/rfc_authority_check.

Running SCI on standard SAP and add-ons

SCI is a very powerful code scanning tool (see blog). Unfortunately you cannot apply it to standard SAP and add-ons.

Analyzing standard SAP code is the responsibility of SAP, and they take good and secure code (since they provide good code, it is weird they don’t allow everybody to scan their code…). Unfortunately a lot of add-on providers do not.

The blog will explain how to scan code of standard SAP and mainly on add-ons.

Questions that will be answered are:

  • What is the background on not being able to scan standard SAP and add-on code?
  • Can I truly scan the code of a new OSS note 7 days?
  • How can I work around these restrictions and still scan the code of an add-on?

Background

The background of not being able to scan standard SAP code is explained in OSS note 1986391 – Using SLIN/SCI to check SAP standard objects. This note also explains you can scan OSS notes and transports for 7 days. After that time it is no longer possible. Unfortunately this rule also applies to add-ons.

Why run SCI on add-ons?

Why would you want to scan add-ons? Add-ons come with various quality levels. Ranging from very well written with much attention to performance and security. Some add-ons are full of performance issues and full of security leaks. Some are even allowing full dynamic read SELECT and UPDATE statement without any authorization check. This is heaven for a hacker!

The below method is meant for scanning these poor add-ons using the SCI tool for performance, robust coding and security.

How to run SCI on add-ons?

When you run the SCI tool on an add-on by selecting package or development object, you get the message that it does not contain any objects:

This is because your selection is first scanned for standard SAP and add-on objects. These are removed. So the result set is empty.

Goto transaction SE24 and select class CL_CI_OBJECTSET. Now select method BUILD_TADIRSET and display the code:

Put a break-point as statement if ENABLE_CI ne ‘X’.

Now start the SCI tool again. If the debugger stops at this statement, use debug and replace to change the content of ENABLE_CI to ‘X’. Now the skipping of SAP and add-on objects is not done. SCI will scan the code. It will still not use SLIN. But these are minor checks.

Load balancing settings

Larger productive systems have multiple application servers to spread the workload. But if the system is not configured properly one application server can be overloaded while others are almost idle. This blog will explain the load balancing settings.

Questions that will be answered are:

  • How can I check my current load balancing situation?
  • How can I load balance SAP GUI users?
  • How can I load balance SAP to SAP RFC traffic?
  • How can I load balance external system to SAP RFC traffic?
  • How can I load balance qRFC traffic?
  • How can I load balance batch jobs?
  • How can I load balance web traffic?
  • How can I configure MRP parallel processing settings?

How to check current situation of load balancing

You can start transaction AL08_OLD (in older systems AL08) to get an overview of the distribution of your logged on users and how they are spread over the application servers:

Load balancing for GUI logon

With transaction SMLG you can setup logon groups that can be used for SAP GUI logon and RFC logon. In the details of each logon group you can make dedicated settings:

The Fav.Typ setting indicates the load balancing mechanism (round robing, best performance, weighted round robin). Set Ext RFC-enabled to also do load balancing in this group for external RFC calls.

You can set limits per application server on response time and amount of users. This limit is not a hard limit, but a soft limit to influence the quality calculation. The setting is per application server and it is across the logon groups (you cannot make settings per logon group). The background of these limits is explained in OSS note 118093 – Concepts of defining ‘limits’ in logon load balancing and on the SAP wiki page.

In SMLG you can choose menu option Goto / Load distribution to get an overview of the current load distribution and quality:

A higher quality number means it has the best quality. New users that logon will be routed to this server if you have set the SMLG settings to Best Quality.

Relevant OSS notes:

RFC traffic load balancing for SAP to SAP connections

For SAP to SAP connections using RFC you have to set the load balancing to Yes in SM59 and fill out the proper message server and logon group details:

RFC traffic load balancing for external system to SAP connections

Many external systems connect to SAP via the SAP JCO connector. The JCO connector can do load balancing, if configured properly. The problem here is that the developers form the other application using JCO have no idea on the settings to be made. The other problem is that on a development system the settings are typically pointing to one server only and the basis team did not configure load balancing. Now suddenly in production (or in a quality environment) they have to switch to load balanced settings using different parameters.

The parameters settings to be made are explained in:

Tips for basis team:

  • Also setup the logon group in development system and assist the external team with the needed settings. The best way is that the external team uses load balancing settings from the start in development as well
  • Setup extra application server in quality landscape to test load balancing

RFC server group

With transaction RZ12 you can setup RFC server groups that also can be used for load balancing purposes.

RFC load balancing for qRFC

If you use qRFC (this is used for example in the CIF interface to SCM and EWM), then you need to configure the RFC group (settings made in RZ12) in transactions SMQS and SMQR. See blog on qRFC.

Web traffic load balancing

For web traffic load balancing, you have to set up the SAP web dispatcher. In the SAP web dispatcher you can configure to which back-end application servers to use.

Batch job load balancing

Batch job load balancing can be done by setting up batch job server groups in transaction SM61. See this blog.

MRP run parallel processing

The MRP run (material requirements planning) is a very intensive process from the system perspective and very important from business perspective. It is important that the MRP run finishes in time, but is also should not overflow the system by occupying all work processes and CPU. In this customizing action you can defined the MRP run parallel processing settings:

Now you can assign the specific application servers that the MRP run is allowed to use in parallel and the maximum amount of work process it can use:

Troubleshooting OSS notes and blogs

The following OSS notes can be useful for troubleshooting:

Useful background blogs:

Workflow tips & tricks

SAP workflow is used for many different business scenarios. This blog will give tips and tricks for the basis part of SAP workflow.

Questions that will be answered in this blog are:

  • How can I send a reminder email to the workflow owners?
  • How to check how many items in the inbox a user has?
  • How to delete the items in the inbox of a user?
  • How can I terminate workflow(s) as administrator?
  • How do I execute general workflow activation?
  • Where can I find more FAQ and manuals on workflow?
  • How to solve workflow transport issues?
  • How can I add a general task to a transport?
  • How can I setup forwarding of workflow as admin?
  • How can I check if a user has setup a substitution?

Workflow FAQ note

SAP has created an excellent FAQ note: 2214571 – Collection Note: Workflow troubleshooting guides, FAQs and important notes. This is a good starting point for find solutions to workflow issues.

Sending reminder email to workflow owners

Program RSWUWFML2 can be used to send reminders to workflow owners that they still have open workflow items:

It is important to know that only reminders will be send in mail if the workflow owner user ID’s mail address in maintained in SU01.

Important explanation OSS note:

Important bug fix OSS notes:

Changing the message subject of the reminder mail

To change the message subject of a mail, create a new message in SE91. Example is class Z_CUSTOM message 010 with text: “Gentle reminder of workflow”. Now put in field message class for subject field the name of your class (Z_CUSTOM) and the message number in message number for Subject:

Changing the body of the message of the reminder mail

Goto transaction SE61 and select text type Text in Dialog. First the default text SWU_NOTIF_INBOX:

Now use the copy button to copy the text to a Z text. For example Z_SWU_NOTIF_INBOX. Change the text as per you requirement and activate the text.

Now you can use this new text in the workflow reminder mail program:

SAP workflow inbox

Using transaction SOY5 or via program RSSOINBO you can get an overview of the amount of workflow items per user:

Via program RSSOINBD you can delete the inbox of a user:

Terminating workflows as administrator

Start transaction SWIA:

In the second screen select all the items you want to terminate and use menu option Edit / Work Item / Logically Delete. The workitem will now to status CANCELLED.

See also oss note 2422812 – How to delete workflow item from inbox.

Reducing size of workflow tables

Workflow tables start with SWW. They can grow very large in a productive environment. For analysis see blog. For deletion and archiving see blog.

Basic workflow activation in a new system

For activating workflow in a new system or after an S4HANA upgrade, please read this dedicated blog.

Transport issues with workflow

Workflow development objects can give some issues in transports, since not all objects are immediately put into a transport upon development.

If you have set a workflow task to general and want to transport it, use program RHMOVE30 to put it into a transport. For more background read this SAP blog.

Substitution and forwarding

Using transaction SBCS_EXTCOM you can setup forwarding for a user ID towards different user ID as admin. This might be needed in case of illness of a user:

In the third tab of this transaction you can see if a user has setup a substitution himself.

Data archiving: store files in SAP content server

With data archiving you reduce the database size of SAP and increase the performance by reducing the amount of records in the SAP tables. The data archiving process write files with the archived data. These files must still be stored securely, since on file level any admin can delete the files and you might loose valuable business data.

This blog explains the setup of storage of data archiving files by using SAP content server as storage medium.

Questions that will be answered are:

  • How do I setup the link from SAP netweaver ABAP stack to the SAP content server?
  • Which settings do I need to make in the archiving objects to store the archiving file to SAP content server?
  • How do I store the files in the SARA transaction?

General tips and tricks for SAP content server can be found in this blog.

How to setup archiving technically can be found in this blog.

How to run archiving can be found in this blog.

Linking the SAP Netweaver ABAP stack to SAP content server

First we need to maintain a special protocol in customizing using this path:

Create a new protocol:

This protocol can now be assigned to the SAP content server you want to use for storing the data archiving files. Goto transaction OAC0 to link the protocol to your content server:

If the field protocol is not visible immediately there, click the button Full administration first.

Data archiving object specific linking

After the steps above to make the general connection to content server available, the content server needs to be explicitly mentioned in each data archiving object. For any data archiving object (start transaction SARA first and select the object), click on the customizing button:

In the popup screen now select Technical Settings in Archiving Object-Specific Customizing:

At the bottom fill out the content server repository and decide if you want to start automatically or immediately:

Remark 1: the F4 search help does not work here! Key in the value directly and check using the check button. Then save the data.
Remark 2: always tick the option Delete Program Reads from Storage System. This forces that the archive file is securely stored first, before the deletion run is allowed to start. 

Storing archive files in SARA

After the configuration is done the new button Storage system appears on the screen in the SARA transaction for this specific object:

Storage system

If the button does not appear: check the technical settings above, and remember: this is to be repeated for each object.

Storing files that have been written by the Write phase of the data archiving process can now be stored by pressing the Archive Files button:

Select the file(s) to store:

Now a batch job starts (per file!) to store the archive file into the SAP content server.

After correct storage of the file, the file can be selected in the delete phase.