Message type: E = Error
Message class:  /SAPAPO/APO -  
Message number: 351
Message text: Choose an application
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.
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The SAP error message /SAPAPO/APO351 Choose an application typically occurs in the context of SAP Advanced Planning and Optimization (APO) when a user attempts to access a function or transaction that requires the selection of a specific application, but none has been selected.
Cause: No Application Selected: The most common cause of this error is that the user has not selected an application from the available options in the APO system.
Configuration Issues: There may be issues with the configuration of the APO system that prevent applications from being displayed or selected. Authorization Issues: The user may not have the necessary authorizations to access certain applications within APO.
Solution: Select an Application: When prompted with the error message, look for a dropdown or selection box where you can choose an application. Make sure to select the appropriate application that you want to work with. Check Configuration: If the applications are not appearing as expected, check the configuration settings
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