Is it really possible to have too much of a good thing? If we are talking about tasks in a SharePoint list, or really tasks in multiple SharePoint lists, then the answer can be 'yes'. Sure, the IntelliGantt Web Part can scale to tens of thousands of task items in one view, but there is the simple matter of loading all that data. Even on a gigabit network, it can take time to pull everything into view.
So we put our heads together with a few of our customers and came up with a setting we call 'Depth Level'. In a nutshell it limits the number of tasks the IntelliGantt Web Part will acquire from SharePoint by putting a limit on the number of times it digs into a Summary Task (or folder in SharePoint 2007). As a result, even though your selection of SharePoint tasks may number in the millions, you quickly retrieve a minimum amount of data (the top level of items) to show useful summary information (start dates, end dates and percent complete).
Let's take a look at how it works. Below is a screenshot of a SharePoint site containing two task lists with considerably less than one million tasks. However, notice that there are summary tasks containing child tasks.
We can configure the IntelliGantt Web Part so that it gets just the top level summary tasks by setting the Depth Level. To do so, we shall edit the web part properties. Inside the 'IntelliGantt' category, we see the 'Depth Level' field.
You may wonder what Collapse Level is right above Depth Level. Collapse Level is different in that it sets how deeply to open the hierarchy initially, but will not affect the actual volume of data retrieved from SharePoint. Collapse Level is the right choice when you want a summary view, but also would like to burrow into all the details. The Depth Level is for a summary view that can load Right Now.
Let's set the Depth Level to 1...
... and see what we end up with.