The Database Utility is used to create, delete, set default identity and rebuild an identity. To access the Database Utility, hold down the Option key when launching Outlook. You can also find the Database Utility in the Microsoft Office 2011 folder in the Office folder.
/Applications/Microsoft Office 2011/Office/Microsoft Database Utility.app
Rebuilding should be avoided unless there is database corruption. If your Identity will open, rather than rebuild, try exporting your data and move to a . . .
Continue Reading: Basics for a Successful Rebuild