I call RecordManager.update(recid, data) many times. Each time the data I use is larger. After each update I commit. The database file .db grows very fast. It appears that none of the previous values is deleted from the file, so in the end the file is huge.
I attached patch to TestRecordManager that shows the problem. It adds new record of size 1000 bytes. Then it updates this record with new data. Last data's size is 25950 bytes. But the file .db is ~6,5 MB.