Forecast Reporting where you have Actual for Jan-Feb and Forecast Mar-Dec?
There are a couple of ways to approach this. As a data issue within the database and as a reporting issue. Many older products only allowed you to handle it in the reports, but there are limitations in that. So let me explain how to do both.
In the database, typically as you close actuals each month, you copy your actuals to your forecast scenario. This has the advantage of then having a full Forecast with easy reporting of YTD, calculations, etc at the database level for easy user reporting and interaction. So then you just report against the Forecast scenario and what you see are actuals up through the latest period and forecast for all the future periods.
Often companies will also have additional Forecast scenarios so they can look at the current Forecast vs prior Forecast scenarios to see how they have changed over time.
The only down side to this approach is that your Actual data may have data for many more accounts than typically are used for Forecast, but this is just a volume issue that does not worry me. You would want to insure that any Forecast only accounts roll up to the correct summary level accounts for consistent reporting. This is something to insure no matter what approach you take.
Now on to the Reporting approach. For the reporting approach, you want are report that shows time periods in the columns, where the time periods for part of the year show data from Actuals and the rest of the year show Forecast. This is easy to do, but it has the restriction that just like any other product it only works for Periodic data and when the total year number is calculated in the report with a SUM function.
To do this kind of reporting, the simplest thing is to add Member property to the Time dimension to contain the Scenarion to use for each Time period. Then in the report define a CV Override on the Scenario based on the property from the Time dimension. Then each month, they simply update that property in the Time dimension.