You don’t… We have had this question a couple of times so thought it worth a posting. Customers and partners familiar with Project Server 2013 or even Project Server 2010, may be used to copying the databases to another server for testing or reporting or whatever. In Project Online that certainly isn’t an option. You have 3 PWA instances available to you so you could use one for testing – but there is no way to get access to your databases or copying them either within or in/out of the datacenters. You do of course have access via OData to much of the information in Project Online and could pull this down to a local data store for other reporting purposes – or through CSOM as described in the Project SDK. The OLAP cubes aren’t an option in Project Online – so if you wanted an OLAP capability then getting data locally (or somewhere else in the cloud – SQL Azure for example) via one of these mechanisms would enable you to use other reporting tools. You can of course save project plans down to mpp format locally too. This last point is worth considering for archive purposes – as the administrative backup options are not a feature of Project Online (as mentioned in Tuesday’s Server Settings post).
There are also 3rd party options that may help get at your data (just Bing Project Online migration tools) – and so far FluentPro appear to be coming highest up the search results. I’d certainly love to hear from other partners if you have interesting offerings too. Migration can be about getting data into the online environment – but the same kind of tools usually offer opportunities for pulling data out too – whether for reporting – or perhaps you are using the Online environment for a proof of concept which is fore-runner to a Project Server 2013 on-premise installation!
Finally, a good article if you want to build your own tools is the SDK and worth starting at the comparison of Project Online to Project Server 2013 from a development perspective.
As I have mentioned previously – Project Online is a close relative to Project Server 2013 but not an identical twin – learn to think of them as different products with different feature sets.