You should properly secure the databases, platforms, and servers you use for your P6 Professional. You might find the links below helpful when planning your security strategy.
Oracle Database 12c
https://docs.oracle.com/database/121/nav/portal_25.htm
Oracle Linux Security Guide
http://www.oracle.com/technetwork/articles/servers-storage-admin/secure-linux-env-1841089.html
Microsoft Windows Server 2012
https://technet.microsoft.com/en-us/library/jj898542.aspx
Microsoft SQL Server 2012 Database
https://msdn.microsoft.com/en-us/library/bb283235(v=sql.110).aspx
Microsoft SQL Server 2014 Database
https://msdn.microsoft.com/en-us/library/bb283235(v=sql.120).aspx
Note: This is not a comprehensive list.