Hi Guys, here is some good stuffs.

Both P3 and P6 are project management tools that allow users to plan and control projects with a high degree of accuracy, keeping them on time and under budget. However, P6 includes the addition of a number of new features requested by our user-base including the ability to track and unravel multiple float paths, enhanced graphical reporting with features like multiple, formatable curtains, and the long awaited option to UNDO! New features and enhancements will continue to be added to this product with each successive release.
While P3 maintains each project as a separate group of files–each existing completely independently of the others–P6 stores all projects in a single database, allowing greater flexibility to view, manage, and analyze projects singularly, as part of a master project, program, or enterprise. This single database design increases efficiency, consistency and repeatability, saving organizations time and money.
Additionally, while P3 has used the extremely reliable Btrieve database engine since 1985, its 16-bit technology is quickly becoming outdated. Due to technological limitations and other factors, development of P3 has been discontinued. P6 is built using the platform of the future. Project data is stored in a central project database that resides on a server running Microsoft SQL Server, SQL Express, or Oracle. This type of relational database management system offers many advantages over the file structure system used in P3. For one, not all projects are managed separately—because data is stored in a central database, rather than on the user’s PC, P6 enables managers to access project data anywhere, at any time.

Suresh