Performance issues caused by SQL statements in ASP

Today, modified a little last done in the office management System file upload bug, because the ASP SQL statement performance problems caused the Recordset object closed, the result of data warehousing failed. For this error, I can only now understand that:
When the SQL statement select * FROM Tab_files opens the table, and then calls the AddNew method to add the data to be updated, there is no problem on the surface, and the select * from Tab_files problem is exposed when the Tab_files table is recorded quite a few minutes, All selected data is written to the system memory buffer (the actual operation is completed by the Recordset), and the Recordset is shut down when the amount of data fetched from the database exceeds the threshold that the buffer can hold, and the final data warehousing of course fails.
I used a temporary workaround: Reconstruct an SQL statement that does not return any records, just like opening an empty table, and then the database update operation.