Message type: E = Error
Message class:  /PM0/ABP_BTX -  
Message number: 201
Message text: TEST: BTrans (&1) will be executed in "old world" due to user parameters
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 /PM0/ABP_BTX201 TEST: BTrans (&1) will be executed in "old world" due to user parameters typically indicates that a business transaction (BTrans) is being executed in a legacy mode or "old world" mode due to specific user parameters set in the system. This can happen in various SAP modules, particularly in the context of business transaction processing.
Cause: User Parameters: The error is primarily caused by user-specific settings or parameters that dictate how transactions are processed. If a user has set parameters that are incompatible with the new processing mode, the system defaults to the old processing mode. Configuration Settings: The system configuration may not be aligned with the new processing standards, leading to a fallback to the old mode. Legacy System Integration: If the system is integrated with legacy systems, certain transactions may need to be processed in the old mode for compatibility reasons.
Solution: Check User Parameters: Go to the user
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
/PM0/ABP_BTX200 TEST: BTrans will be executed in "old world" due to user parameters
What causes this issue?  <ZH>ONLY RELEVANT FOR TEST PHASE:</> During the MIT test phase, it is possible to branch to the previous process ...
/PM0/ABP_BTX196 Category '&2' of field modifier for entity '&1' does not exist
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
/PM0/ABP_BTX202 TEST: Subprocess will be executed in "old world" due to user parameters
What causes this issue?  <ZH>ONLY RELEVANT FOR TEST PHASE:</> During the MIT test phase, it is possible to branch to the previous process ...
/PM0/ABP_BTX203 TEST: BTrans will be executed in NEW world, on basis of user parameters
What causes this issue?  <ZH>ONLY RELEVANT FOR TEST PHASE:</> During the MIT test phase, it is possible to branch to the previous process ...
Click on this link to search all SAP messages.