It is not always possible to have a steady connection to the internet. Offline mode uses the Primavera Cache Service to allow you to continue working in P6 Professional while your internet connection is unavailable. When internet connectivity is restored, click 
Connect to Cloud to reconnect to the cloud database and synchronize the data in the local cache database with the Cloud Connect database.
Notes:
- To work offline, you must connect to the Cloud Connect database using an alias which has the client-side cache enabled and log into P6 Professional as a user with the relevant security privilege. Administrative settings also control the availability of the option to work offline.
- Oracle recommends you reconnect to the cloud database at least once a day, but preferably as soon as internet connectivity is restored. Reconnecting to the cloud database allows the local cache database to synchronize with the Cloud Connect database to minimize the possibility of data loss.
When you are working in P6 Professional, you can choose to work offline at any time, either by selecting the 
Work Offline option on the file menu, or selecting the Work Offline button on the toolbar. When you are ready to go back online, use the Connect to Cloud file menu item or toolbar button.
Whether you have chosen to go offline or have been forced into offline mode by losing your connection to the internet, a status bar indicator shows whether you are working offline or online.
If you close P6 Professional while you are working offline, the next time you open P6 Professional the login dialog box shows a Work Offline option. If you want to continue working offline, ensure the option is selected before you log in. Alternatively, clear the option to log into the Cloud Connect database and work online.
When you are working offline, some features will be unavailable, including: Copy Project when your view is sorted by EPS, Create Baseline, Update Baseline, Import XML, Apply Actuals, Summarize, Check In/Check Out, and Create Reflection.