Message type: E = Error
Message class:  CNV_CMIS_A_20 - Message class for Cross-Client Customizing Comparison (SLO) 
Message number: 287
Message text: Select a table to be excluded from content comparison
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 CNV_CMIS_A_20287 typically occurs during the content comparison process in the SAP system, particularly when using the SAP Conversion Management Information System (CMIS) tool. This error indicates that the system requires you to select a table that should be excluded from the content comparison.
Cause: The error arises when the content comparison process is initiated, but the system does not have a specified table to exclude from the comparison. This can happen due to:
Configuration Issues: The configuration for the content comparison may not be set up correctly, leading to the system not recognizing any tables to exclude. User Input: The user may not have selected any tables to exclude, or the selection may not have been saved properly. System Limitations: There may be limitations or restrictions in the current version of the SAP system that prevent the selection of tables.
Solution: To resolve the error CNV_CMIS_A_20287, you can follow these steps: Select a Table:
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV_CMIS_A_20286 Worklist is Empty
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_CMIS_A_20285 Following Application tables are included for comparision.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_CMIS_A_20288  Sorry! Selected list contains already excluded table entries.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_CMIS_A_20289 Please select comparable table entries and go ahead
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.