Application of SAP XI Technology in Integration of ERP and MES

The XI (Exchange Infrastructure) technology newly developed by the German SAP company provides a good system integration environment for enterprises. Based on the XI technology, enterprises can achieve full integration at all levels. The author will explore the application of XI interface technology in the integration of enterprise ERP and MES based on the information transformation project of Handan Iron and Steel Group, the first company in China to successfully apply SAP XI technology.

1 XI Technology

SAP XI is one of the core components of SAP's open integration platform NetWeaver. It integrates and develops two connection methods: middleware and BC (Business Connector). The following will introduce XI technology from three aspects: function, structure and connection method.

1.1 Functionality

Based on xI technology, enterprises can reduce the overall cost of information system construction and achieve integration in the following four aspects. The first level is to centralize existing management systems, office systems, document systems, etc. into the enterprise's information portal to achieve a single entrance to the enterprise's IT system. This level is called "employee integration." The second level is to centralize various management information stored in the database and unstructured information (market information, reports, and other document information) scattered in different places within the group to achieve an information warehouse (BI) and knowledge management system that supports business decisions. This level is called "information integration" [2]. The third level is to enable components in different environments to interact in communication and enable customers to model and apply new businesses in a dynamic IT environment in business process management. This level is called "process integration." The fourth level is to provide an underlying architecture that supports open standards (such as XML) to achieve flexible interconnection between the enterprise's existing information system and various original systems brought about by acquisitions and cooperation. This level is called "platform integration."

1.2 Overall Architecture

In the overall architecture of XI technology (see Figure 1), the integrated knowledge base is used for business scenario analysis and system design; the integrated directory is used for the configuration and management of XI objects; the system platform directory is used to save and manage system instances created for business scenarios; and the integrated server is used to establish message types, determine logical routing rules and technical routing rules, and select and design ABAP Proxy calls.

1.3 Connection method

In terms of the connection method with other systems, xI technology adopts a star connection method with XI as the central hub. All systems to be connected only need to connect to xI once, thus avoiding the problem of a sharp increase in the complexity of system integration when multiple systems are connected (need to connect N×(N-1) times) caused by the one-to-one connection method between middleware and application systems under BC. In addition, xI converts all data formats sent from the source system into XML format for processing, determines its target system, and converts the data from XML into the format required by the target system for output, which can effectively realize the communication integration between SAP and different systems.

2 XI Implementation Process

In the Handan Iron and Steel SAP R3 and MES integration project, according to the needs of each business module, the data information exchanged through the xI interface is determined to include the following categories.

(1) Data transferred from Level 4 R3 to MES, including material master data, customer master data, picking lists, production orders, etc.

(2) Data uploaded from MES to R3, including quality inspection judgment, production receipt, material movement type accounting, etc.

(3) Data transmitted between the three levels, including factory-to-factory purchase orders, material transfer orders between the three levels, etc.

According to Handan Iron and Steel's business processes and xI technical characteristics, the implementation process of this project includes the following steps.

(1) Business scenario analysis. Describe the business scenario to be implemented and the backend systems involved in the business, determine the interface strategy (create a new interface or modify the original interface), design the technical architecture, functional architecture and xI architecture of the business, and create a system entity model in the SLD (System Landscape Directory).

In view of the needs of each business module in the ERP and MES integration project of Handan Iron and Steel, the business scenarios can be described as follows: 1) Create a sales order in the SAP system; 2) Perform availability check; 3) Generate a planned order; 4) Convert to a production order; 5) Create corresponding data in MES; 6) Create a corresponding delivery note after production is completed. The data transmission of the above scenarios is realized on the xI data platform, and the reception of data is managed by more than 100 interfaces.

(2) Interface analysis. Determine the following characteristics and parameters of the interface: the real-time nature of the interface (synchronous or asynchronous), whether the interface requires technical or application-level response confirmation (closed loop or not), the import and export message types of each interface, the data structure of each message type, the format of text files, the structure of the database, IDoc (Intermediate Document), RFC (Request for Comments), BAPI (Business Application Programming Interface) structure, and XML data structure, provide data samples for each message type, and create message object entities in the integrated knowledge base.

Taking the production order management process as an example, its interface is shown in Figure 2.

(3) Mapping definition: Determine the mapping rules of the interface based on the results of the interface analysis, select the technology to implement the mapping (graphic tool, JAVA, XSLT) and implement the mapping according to the defined sample rules.

(4) Environment preparation. This includes test environment definition and test environment preparation. Test environment definition includes configuration of proxy servers and definition of network hardware connectivity. Test environment preparation includes completing system installation and checking xI services after installation, creating users, assigning user permissions, etc. If it is to prepare for going online, the online switching strategy must also be defined and uploaded in the order of development machine, test machine, and production machine.

(5) System configuration. Configure the backend system to ensure that the system can generate and receive data that is the same as the sample data, and configure the xI object and xI integrated directory in the integrated directory based on the results of steps (1) to (4).

(6) System testing: Use different data sets to conduct point-to-point business scenario testing and online switching testing.

After completing the above steps and collecting various data, configure the system environment and complete the following tasks: set up integration scenarios, establish message types, determine business systems, determine logical routing rules, determine technical routing rules, call ABAP Proxy, and use JavaServer Proxy.

3 Key issues and solutions

As an emerging technology, xI is applied in China for the first time. Its successful operation has well supported the implementation of Handan Iron and Steel ERP project, and has a great reference and driving role in data integration and data communication in domestic information construction. The following will describe the multi-system communication and data congestion problems encountered in the implementation of the system and their solutions.

3.1 Multi-system communication issues

The information project of Handan Iron and Steel Group includes multiple three-level systems, among which the three-level communication is realized through two methods: DB To DB and Web Servers (such as Tomcat). How to integrate the communication method of xI with other Web Servers is an important issue to be solved in the implementation of the system.

Since xI itself has a Web Application Server mechanism, the currently common SOAP protocol is used in the communication method with other Web Servers. That is, Tomcat organizes XML data and sends the data to xI through the SOAP protocol. The specific implementation process is as follows:

Establish XML Schema, connect XML document instances to XML Schema, SOAP converts XML usage codes into request and response parameter encoding patterns, and uses HTML for transmission [3]. A SOAP method can be simply regarded as an HTML request and response that follows SOAP encoding rules. A SOAP endpoint can be regarded as an HTML-based URL used to identify the target of the method call. Like Corba/IIOP, SOAP does not require specific objects to be bound to a given endpoint. Instead, it is up to the specific implementation program to decide how to map the object endpoint identifier to the server-side object. The SOAP request is an HTML POST request, which must be of type text/xml and must contain a request.URI. The way the server interprets this request.URI is related to the implementation method of the request.

3.2 Data congestion problem

Since the connection between xI and the three-level system is a one-to-many relationship, the xI system corresponds to multiple systems, and the data transmission adopts a queuing mechanism. Therefore, if the data is not prioritized, the order of transmission is first in, first out. When the transmission communication fails, xI will automatically reschedule the communication until the scheduling reaches a certain number of times (configurable), then it will determine that the communication has failed and schedule the next interface. The data is saved in the database for manual scheduling. Under normal circumstances, the xI queue can process multiple data concurrently, but once any receiver of the transmitted data is abnormal, such as network interruption, database deadlock, etc., the repeated scheduling of data due to a single point failure will cause the data queue to be too long, the system overhead will increase on a large scale, and then a single point failure will cause data congestion.

In order to solve the data congestion problem caused by single point failure, the project combined XI's data distribution mechanism with existing equipment during implementation, established a distributed architecture, and configured the interfaces prone to data anomalies to the shunt machine, as shown in Figure 3.

Since the diversion system in the project uses HP's minicomputer HP4640, the operating system is HP-ux, the data is Oracle, and the data of OS/400 is DB2, the JVM mechanisms of the two systems are very different. Therefore, the data of the diversion system is mainly stored in Oracle, and the data is directly dispatched from Oracle instead of DB2. When a problem occurs at a certain receiving point, the problematic data can be thrown to Oracle, and the data can be manually triggered to be downloaded when the receiving point returns to normal. This method will not affect the normal download of data in other queues.

3.3 Implementation Effect

The data communication of Handan Iron and Steel Group's information technology project is not only complex in design, but also has large data traffic and high data pressure during peak business hours, which puts great challenges on hardware and software. The effective implementation of XI technology ensures the effective transmission of data and significantly improves the response speed to abnormal events. At present, the average data business volume remains at 10,000-15,000 synchronous data and 8,000-12,000 asynchronous data per day. The current system configuration optimizes system performance while meeting business needs and realizes the integration and optimization of business systems.

4 Conclusion

As the latest communication technology module of SAP ERP products, XI technology has been favored by users since its launch. Many foreign SAP users have adopted the XI communication platform to connect SAP systems and non-SAP systems. Although XI technology has been widely used abroad, its application in China is still blank. The successful application of XI in Handan Iron and Steel's informatization transformation project has a good guiding significance for the enterprise's informatization construction.