Message type: E = Error
Message class:  /SAPAPO/STOR_MSG -  
Message number: 027
Message text: User &1 is currently processing plan &2
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.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message /SAPAPO/STOR_MSG027 indicates that a user is currently processing a specific planning object (in this case, a plan) in SAP Advanced Planning and Optimization (APO). This message typically arises when multiple users attempt to access or modify the same planning object simultaneously, leading to a conflict.
Cause: Concurrent Access: Another user is currently working on the same planning object, which locks the object for editing. Long Processing Time: The user currently processing the plan may be taking longer than expected, causing others to be unable to access it. System Configuration: The system may be configured to prevent multiple users from editing the same plan at the same time.
Solution: Wait and Retry: The simplest solution is to wait for the other user to finish processing the plan and then try again. Check User Status: If you have the necessary permissions, you can check which user is currently processing the plan. This can often be
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
/SAPAPO/STOR_MSG026 Error while converting product quantity; verify unit conversion rules
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
/SAPAPO/STOR_MSG025 Product flow is maintained for the source of supply
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
/SAPAPO/STOR_MSG028 All components are already assigned to SOS
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
/SAPAPO/STOR_MSG029 Resource & is not maintained with planning version &2 of SOS
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
Click on this link to search all SAP messages.