Questions about Back-end

1. you have several options one of the most powerful things in P6 is having the ability to create codes and assign the different codes to the activities like attributes. You could create an activity code call it phase and have a code value such as ENG or engineering, PROC for procurement or CON for construction. The you assign the activity to one of these 3 groups and then you can filter and or group and sort on any or all of the codes that you have assigned.

2. The way to capture ANYTHING in a time sensitive snap shot is to take that snap shot before something changes. One of the things that I do is before I make any major change is I select send project. This automatically open my default email program and attaches an Primavera xer file in my email. Then I email this file to myself. This way if something goes bad I always have a prior version.  

JS,

1) Wow. Almost no one on here works, or indeed would want to work with the raw tables. Even the geeky ones would be using the API or web services in applications not the data tables per se.

2) P6's transaction tracking is poor. I am not an expert on it, when designing solutions I look elsewhere to keep history. P6's application layer "Baseline" facility keeps a snapshot of a project when you ask for it. However the application only permits certain values (typically numeric calculated fields like Start Date) to be refernced using the client software - but it does hold previous WBS codes. I have no idea how I would view the history of those without SQL skills none of us planners have!

well, all activities are stored in the ADMUSER.TASK table. but it helps to follow the ACTVTYPE --> ACTVCODE --> TASKACTV tables as well. (to help pinpoint the code you are looking for) 

i don't know the answer to your second question.