How To Fix ME521 - Session &: 1st transaction does not begin with a header record (type 1)

SAP Error Message - Details

• Message type: E = Error

• Message class: ME - Purchasing: General Messages

• Message number: 521

• Message text: Session &: 1st transaction does not begin with a header record (type 1)

Self-Explanatory Message

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Smart SAP Assistant

• What is the cause and solution for SAP error message ME521 - Session &: 1st transaction does not begin with a header record (type 1) ?

  The SAP error message ME521, which states "1st transaction does not begin with a header record (type 1)," typically occurs during the processing of inbound IDocs (Intermediate Documents) related to purchasing documents. This error indicates that the first transaction in the IDoc does not start with the expected header record, which is necessary for the system to correctly interpret the data.
  Cause:
  
  Incorrect IDoc Structure: The IDoc being processed does not conform to the expected structure. The first segment of the IDoc should be a header record (type 1), but it is missing or incorrectly formatted.
  Data Corruption: The IDoc data may have been corrupted during transmission or processing, leading to an invalid format.
  Configuration Issues: There may be issues with the configuration of the IDoc type or message type in the SAP system, leading to mismatches in expected data formats.
  Custom Development: If there are custom developments or enhancements related to IDoc processing, they may not be handling the data correctly.
  
  Solution:
  
  Check IDoc Structure: Verify the structure of the IDoc being processed. Ensure that the first segment is indeed a header record (type 1). You can use transaction WE02 or WE05 to view the IDoc and its segments.
  Validate Data: Ensure that the data being sent to SAP is correctly formatted and adheres to the expected IDoc structure. If you are generating the IDoc from an external system, check the generation logic.
  Review Configuration: Check the configuration of the IDoc type and message type in transaction WE30 (IDoc types) and WE81 (message types). Ensure that they are set up correctly and that the mappings are accurate.
  Error Handling: If the IDoc is being processed in a batch, check for any previous errors that may have affected the current IDoc. Address any issues found in prior IDocs.
  Consult Documentation: Refer to SAP documentation or notes related to the specific IDoc type you are working with for any known issues or additional troubleshooting steps.
  Testing: If changes are made, test the IDoc processing with a sample IDoc to ensure that the issue is resolved.
  
  Related Information:
  
  IDoc Types: Familiarize yourself with the specific IDoc type you are working with, as different types may have different structures and requirements.
  Transaction Codes: Use transaction codes like WE02, WE05, and WE19 for monitoring and testing IDocs.
  SAP Notes: Check SAP Notes for any known issues or patches related to the IDoc type you are using.
  Support: If the issue persists, consider reaching out to SAP support or your internal SAP team for further assistance.
  
  By following these steps, you should be able to identify the cause of the ME521 error and implement a solution to resolve it.