Need help in finding a creative solution.

I have an application on hand that processes files coming from a telephone exchange. The approximate file size is about 500,000 rows. I load the file into a table, I then generate a temporary table that sums up the calls per unique telephone number. I then have to update the up-to-date table which indicates how much each telephone number owes up to this processed file. I process about 15 files a day. The update is simple: update amount = amount + new_amount. The challenge is that I cannot chunk the transaction. It all has to be done as one single transaction. If I chunk the logic, one telephone number can be updated twice. The logic works in such a way that if there is any error, it rollsback and continues with the next file. It comes back to the failed file after there are no more files to process. I do not want to run into filling up the log file. This is why I'm looking for a way to chunk. I am using an RDBMS other than Informix. However, I am hoping to find an answer here. Nabil Courdy Senior DBA