Field Mapped as Destination but is Defined as ReadOnly

​​Error Example:

An error occurred while executing connection '<connectionName>': The field '<columnName>' in table '<entityName>' has been mapped as a destination field but it is defined as readonly!

Cause:

This occurs if you have mapped a read-only column in the Target (or for either, in the case of bi-directional) that has to accept data from the Source. As it is read-only, it cannot be written to and produces this error.

There are some special cases where this appears:

• When trying to write to the Create field in OneDrive for Business, but as the account you are trying to use did not have sufficient permissions, that field which is normally writable, was flagged as read-only. This also applies to SPO.
• You had a convert statement in your SQL query, which turned a normally writable field into read-only.
• The Complete.* columns in Exchange are always read-only.
• Some versions of the IBM data providers for AS400 always show the fields as read-only even with they are not. You should try one of the other available drivers, like the i Series ODBC one, to see if that fixes the issue (see Known Issues and Workarounds section of the AS400 Solution page​).
  
  

Resolution/Workaround:

Verify if the mapped field in the error is supposed to be read-only. If so, then you must remove it from the mapping. If not, you should adjust the settings to make it a writable field.

Note that some sources' system columns are read-only and cannot be changed! You will need to create a dummy field to hold that data in the Target data source.

If you are running into this with Exchange CompleteName.* column, you need to use the write-enabled counterpart to the column (if it exists). For example, if you want to update CompleteName.GivenName, then you can map GivenName. Some columns have no counterpart, such as CompleteName.Title and CompleteName.Suffix , so those cannot be written to at all.

If you are running into this issue with SharePoint Online or OneDrive4Business specifically for system fields (such as Created, Modified, Editor, etc.), the account being used to synchronize those fields must have full permissions to the library to do this. It may also require that “AddAndCustomizePages” permission​ has been enabled for the account as well.​ 

When using the Microsoft_Modern authentication you need to change it to Microsoft_Modern_Admin.