It's not easy to do the merge. The computer name needs to be the same. But it's not good to change the computer name in primary database, so we need a 3rd database.
Create an empty temp database. Archive the server2 trace in that time period to the temp database, then in temp database, change the computer name of archived trace to be the same as server1's. Archive the temp database to server1 to merge the data.
You can set the begin and end time for archiving to only archive the missing period, so that in case you make something wrong you won't mess it up.
Ryan Shi
National Instruments