File is opened in read only mode

The file cannot be opened in writing mode

Causes

There may be different reasons:

The file is already open and it is being used; it cannot be opened in writing mode twice:
- Maybe you opened the application more than once and the file was opened in another window.
- Maybe the file has been opened by another user in another session, still active
- Maybe the file is a network shared file, and it is being used by another user
The file is protected:
- Maybe the file is located in a protected folder.
  For example, when you have read-only access to the folder.
- Maybe the file is marked as protected.
- Maybe the fie is located in a system or temporary directory where editing is not allowed.
  This can happen when the file has been opened directly from the internet browser.
- Maybe the file is located on a non writable disk (CD-ROM).

Your modifications cannot be saved on this file, so you have other solutions:

If the file has been opened by someone else, it is better to close the file and open it again when the other user has finished his work.
You can save your modifications by using the Save as command from the File menu, and then saving the data with another file name or in another directory.