The Save options allow you to define where Project will save projects by default, the default format it will use to save projects, and whether it should autosave projects. It's important to note that although Autosave can prevent lots of frustration over lost data, many users choose to keep it turned off because they might not want their edits to be saved automatically, such as when working with "what if" scenarios. Therefore, autosave is disabled by default, but you can enable it here and define how often and for which projects it will save. You can also define whether you should be prompted before each save.
Set Save Options
For nearly all users, the default of Project (*.mpp) is the best choice for the Save Microsoft Office Project option. It defines which file format Project will default to when saving a new project.
To edit which folders Project uses to save project and template files, select one of the entries in the list and click the Modify button.
Use this option to tell Project to save your project every few minutes.
Use this option to tell Project to save the full set of timephased data to the database tables.
For Your Information
Saving Timephased Data
By default, when saving to a database format, Project does not save the full timephased data that it uses to build such views as the Task and Resource Usage views. This is an effort to save time and bandwidth because saving this data can greatly increase the amount of time it takes to save a project. However, without this information being saved in the database, those making queries to the database will not have access to the timephased data. If you are saving to a database and require that the database contain all the timephased data, make sure to check this option.