Message type: E = Error
Message class:  CNV - Conversion: Messages for Conversion Services (CNCC) 
Message number: 777
Message text: Dropping of indexes has already been scheduled by another job
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 CNV777 indicates that there is a conflict in the scheduling of a job that is responsible for dropping indexes during a data conversion or migration process. This typically occurs in the context of SAP's data migration tools, such as the SAP S/4HANA Migration Cockpit or other data conversion scenarios.
Cause: The error occurs when: A job that is responsible for dropping indexes has already been scheduled and is currently running or has been queued. Another job attempts to schedule the same operation, leading to a conflict.
Solution: To resolve the CNV777 error, you can follow these steps: Check Job Status: Go to transaction code SM37 in the SAP GUI. Check for any jobs that are currently running or have been scheduled that involve dropping indexes. Look for jobs with a similar name or related to the data migration process. Wait for Completion: If you find that a job is currently running, you may need to wait for it
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV776 Table &1 has already been dropped by another job
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV775 Lock parameter &1 for table &2 could not be determined
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV778 Some jobs for table &1 are still in the update phase
What causes this issue?  Some jobs for table &V1& are still in the update phase. This means that the indexes must not be re-created yet.System...
CNV779 Creation of indexes has already been scheduled by another job
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.