When you upload position files into FundApps, these represent a snapshot of what each portfolio looks like on that particular day (as defined by NavDate).

If you upload the same portfolio on different NavDates, both will be saved.
If you upload data for the same portfolio on the same NavDate, the first snapshot will be overwritten by the second snapshot.

If you upload a file with multiple portfolios:

(Note that you can only upload for one NavDate per file)
Then you'll receive results for Portfolio 1 and 2, for the NavDate January 3rd 2015.
You then upload:

You'll get results for Portfolio 1 and 2 for the NavDate on January 4th, based on changes in your holdings from January 3rd.

Continuing from Scenario 1:

Portfolio 1 and 2 are part of an Aggregation that includes Portfolio 3 which has, up to this stage, been missing.

As part of scenario 1, you'd have received a result for Portfolio 1 and 2 (if required, but also the aggregated result. You would have also got a breach on one of our validation rules in the UI that would be saying you've uploaded 2 portfolios, but we're expecting one more (Portfolio 3) before the aggregated check is complete.

When you upload a file for the 4th of January just including Portfolio 3:

The engine will run again and include portfolio 3, so you'll get results for portfolios 1,2, and 3, and also the aggregated result. This time, without a breach about missing portfolios.

If during the day, you decide to rerun the following file:

You'll receive updated results again for Portfolio 1, 2, and 3, and the Aggregated result. But this time as if Portfolio 3 only ever had 1 asset in. (It would not update Asset1's quantity from 5 to 1)