How To Fix ATO_CUSTOMER455 - Unknown user &1

SAP Error Message - Details

• Message type: E = Error

• Message class: ATO_CUSTOMER - ATO Messages for the End User

• Message number: 455

• Message text: Unknown user &1

Self-Explanatory Message

Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.

To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.

Unfortunately, there isn't any extra information in this error notice.

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Smart SAP Assistant

• What is the cause and solution for SAP error message ATO_CUSTOMER455 - Unknown user &1 ?

  The SAP error message ATO_CUSTOMER455 "Unknown user &1" typically indicates that the system is unable to recognize or find the user specified in the error message. This can occur in various contexts, such as during user authentication, when accessing certain transactions, or when executing specific functions that require user identification.
  Causes:
  
  User Not Created: The user specified in the error message may not exist in the SAP system.
  User Deactivation: The user might have been deactivated or locked in the system.
  Incorrect User ID: There may be a typo or error in the user ID being referenced.
  Authorization Issues: The user may not have the necessary authorizations to perform the action being attempted.
  System Configuration: There could be issues with the configuration of user management or authentication methods.
  
  Solutions:
  
  
  Verify User Existence:
  
  Check if the user ID exists in the system by using transaction code SU01 (User Maintenance).
  If the user does not exist, create a new user with the required details.
  
  
  
  Check User Status:
  
  If the user exists, check if the user is active and not locked. You can do this in SU01 by checking the user status.
  If the user is locked, unlock the user.
  
  
  
  Correct User ID:
  
  Ensure that the user ID being referenced is correct. Look for any typos or formatting issues.
  
  
  
  Review Authorizations:
  
  Ensure that the user has the necessary authorizations to perform the action. This can be checked in the SU53 transaction after the error occurs, which shows the last authorization check.
  
  
  
  Consult System Logs:
  
  Check the system logs (transaction SM21) for any additional error messages or information that might provide more context about the issue.
  
  
  
  Check Configuration:
  
  If the issue persists, review the configuration settings related to user management and authentication in the system.
  
  
  
  Related Information:
  
  User Management: Understanding how user management works in SAP is crucial. Familiarize yourself with transactions like SU01, SU10 (mass user maintenance), and PFCG (role maintenance).
  Authorization Concepts: Learn about roles, profiles, and authorization objects to ensure users have the correct permissions.
  SAP Notes: Check SAP Notes for any known issues or patches related to user management and authentication.
  
  If the problem continues after trying the above solutions, it may be necessary to consult with your SAP Basis team or SAP support for further assistance.