Message type: E = Error
Message class:  CNV20200 - Messages for development class CNV_20200 
Message number: 254
Message text: &2 mapping entries stored in table &1
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 CNV20200254 typically relates to issues encountered during data migration or conversion processes, particularly when using the SAP S/4HANA Migration Cockpit or similar tools. This specific error indicates that there are mapping entries stored in a particular table that are causing a conflict or issue during the migration process.
Cause: The error message CNV20200254 usually arises due to one of the following reasons: Duplicate Mapping Entries: There may be duplicate or conflicting mapping entries in the specified table, which can lead to ambiguity during the data migration process. Missing or Incomplete Mapping: The mapping entries required for the conversion process might be incomplete or missing, leading to errors when the system attempts to process the data. Data Integrity Issues: There may be issues with the integrity of the data being migrated, such as invalid references or relationships that are not properly defined.
Solution: To resolve the CNV20200254 error, you can take the following steps: Check
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV20200253 &1: CNVINCLTAB entry (&2) was removed
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV20200252 &1 is relevant for other packages; no optimization of &2 is suggested
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV20200255 No renumbering of payment advice line items required
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV20200257 Error while modifying program &
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.