What is RFC and how to create RFC in SAP SM59

• For business applications, it is essential to communicate and exchange information with other systems. SAP has provided a well defined mechanism called RFC (Remote Function Call) to enable this communication.
• RFC Connections in SAP system are used to establish connection with another SAP system or non-SAP system.
• SM59 transaction code is used to create RFC (Remote Function Call) connection.
• There are different types of RFC connections available in SM59 transaction code.

We mainly used to create 2 types of connections in SM59.

1. ABAP Connections (Type 3)
2. TCP/IP connections (Type T) 

STEPS TO CREATE RFC CONNECTION

1. Select 'Create' icon
2. Provide RFC connection details

• RFC Destination: RFC connection name
• Connection Type: For example 3 or T
• Description: Any short description, purpose of the connection

3. Save the RFC connection

NOTE:

Once the RFC connection is saved, it will take us to the tab 'Technical Settings'.

Technical Settings

• Load balancing

Select Yes, if load balancing is configured in system, else

Select No

• Target host: Either Hostname or IP address of the target system
• System Number: System number of the target SAP system

There are 5 tabs available, in which it is required to fill few of the target system details.

1. Administration:

No input is allowed. It just provides the information on who created/modified the RFC and also the corresponding Date/time.

2. Technical Settings: As explained above

3. Logon and Security:

• Language: Target system language, most of the time it's EN
• Client: Target system client number 
• User ID and Password: User details of Target system

NOTE: 

• In general, RFC users can be of any user type
• For security reasons, it is recommended to use only system users for RFC communications, to avoid access to dialog processes.

• Security options:

• Default setting for 'Trusted System' is 'No'.
• If we need the Trusted RFC connection, select 'Trusted System' as 'Yes'.
• This means, the trusted system doesn't need a password to connect with trusting system
• Trusted system = calling system = Source system
• Trusting system = called system = Target system

Some of the features of this option:

• It provides Cross-system SSO (Single-Sign-On) capability
• Password does not need to be sent across the network
• User-specific logon details of the calling system is checked
• Time-out mechanism for the logon data prevents mishandling of logon data

4. MDMP & Unicode:

• On a Non-Unicode system, the settings under this tab are disabled and no changes are allowed.
• This setting is valid only on an UNICODE system, we have to specify the Unicode settings.

NOTE:

If the SAP system is upgraded from Non-Unicode to Unicode, we need to change the communication type to 'Unicode' on all the applicable RFC connections.

5. Special Options:

This option is very rarely used.  For example

• We can activate options for a trace and slow RFC connections.
• To define qRFC

TESTING THE RFC CONNECTION

• Once all the necessary settings are made and the RFC connection is saved, final step is to make sure the connection is established successfully.
• There are 3 types of connection tests are available.

1. Connection test:    

This is the most important. This test is just to check if the calling system is able to reach the remote system. This authenticates the information provided in the RFC connection for target system.

• If the connection is successful, it displays the table with response times. Else
• An error will be displayed with the reason, and troubleshoot is required to fix the issue.

2. Authorization Test:

This test validates the Client, User ID and Password (provided under 'logon and security' tab for the target system).

• If the Authorization test is successful, it displays the table with response times. Else
• An error will be displayed with the reason, and troubleshoot is required to fix the issue (check the logon details and authorizations)

3. Unicode Test:

• This checks if the Target system is an Unicode system or not

RELATED LINKS:

[1] How to change the TMS RFC in SM59

[2] Important RFC tables and reports like RFCDES

[3] RFC Communication types in SAP

[4] Different types of RFC connections

[5] SAP user types

RFC COMMUNICATION TYPES IN SAP

There are 4 types of RFC communication in SAP

1.      Synchronous RFC

2.      Asynchronous RFC

3.      Transactional RFC

4.      Queued RFC

Synchronous RFC (sRFC) :   
In this type of RFC communication, the calling program waits until the requested processing step on the remote system has ended and then continues to work locally.

In other words, both the systems involved must be available at the time the call is made.

Used for

• communication between systems
• communication between SAP Web Application Server to SAP GUI

Asynchronous RFC (aRFC) : 
In this type of RFC communication, the calling program gives the request to the remote system and immediately continues to work locally. 
The requested processing step is executed on the remote system in isolation.

If the remote system cannot be reached at the time of the call, the asynchronous calls of the RFC client are lost.

Used for

• communication between systems
• For parallel processing

Transactional RFC (tRFC) :  
This type of RFC communication is similar to asynchronous RFC but by allocating a transaction id(TID)  it guarantees  that if a request is sent several times because of network problems  it is processed only once. 
Unlike asynchronous RFC,  in Transactional RFC the remote system does not have to be available at the moment the RFC client program start the call. 
The data is held in the source system until the target system is available.

The report program RSARFCSE is called in the background at regular intervals and tries to place the unsuccessful requests, identified by their transaction id again.

Used for

• Extension of Asynchronous RFC
• For secure communication between systems

Queued RFC (qRFC) :  
This RFC communication is an extension to the transactional RFC. 
In this method, all the requests are queued up(inbound queue and outbound queue) and are processed in a sequence only if it is certain that all preceding calls are processed correctly. 
This method guarantees that all the requests are processed in the sequence in which they are received.

This type of RFCs will be used in SCM (APO) systems for CIF queues etc where requests have to be processed in an order.

Used for

• Extension of the Transactional RFC (tRFC)
• For a defined processing sequence
• Implementation of qRFC is recommended if you want to guarantee that several transactions are processed in a predefined order.

RELATED LINKS:
[1] What is RFC and how to create RFC in SAP
[2] Important RFC tables andreports like RFCDES
[3] RFC Communication types in SAP
[4] Different types of RFCconnections
[5] SAP user types

SAP user types

There are 5 user types available in SAP

1.      Dialog

2.      Communication

3.      System

4.      Service

5.      Reference

Dialog:  This is the most commonly used type. This user type is primarily for individuals to gain interactive system access.  A user of this type can perform dialog processing in interactive mode, background processing, batch input processing and CPI-C services provided there are no explicit restrictions via assignment of specific authorizations.

SAP licensing can prohibit multiple concurrent use of the same user id in production SAP systems.

Communication:  This user type is used for dialog-free communication between systems such as RFC (Remote Function call) communication. This user is not allowed to logon to the R/3 system or start dialog processing

Example: TMSADM

System: This is the user type which can be used for dialog-free communication within a system (such as for RFC users for ALE, TMS, workflow and CUA) and for background processing.

A specific use of the system user type is validity period of a password won’t apply for this type. So, this can be used to run background jobs and in between RFCs so that jobs or RFC communications won’t fail due to expiry of the password.

Please note that logon in dialog is not possible.

IMPORTANT NOTE:

In general, RFC users can be of any user type, but for security reasons it is recommended to use only system users for RFC communications.

This is to avoid accessing dialog processes.

Service: This user type is a dialog user which is available to a large, anonymous group of users. For example, to access via ITS (Internet Transaction Server)

There won’t be any check on initial password or expired passwords for this user type. Also, multiple logons are explicitly permitted for this user type.

However this user type should be assigned with great caution and with limited authorizations for security reasons.

Reference:  This user type is in general, non-person related user.  This user type cannot be used for logon. Instead this user type will serve as a reference for assigning additional identical authorizations to other users.

For example: In case you have to assign some identical authorizations to all internet users, you can create a reference user with those authorizations and use this reference user to assign identical authorizations to all other users.