Even with all the work in Microsoft Jet 3.0 to eliminate transactions in order to obtain better performance, SQL DML statements were still placed in an implicit transaction. In Microsoft Jet 3.5, SQL DML statements are not placed in an implicit transaction. This substantially improves performance when running SQL DML statements that affect many records of data.
Although this change provides a substantial performance improvement, it also introduces a change to the behavior of SQL DML statements. When using Microsoft Jet 3.0 and previous versions that use implicit transactions for SQL DML statements, an SQL DML statement rolls back if any part of the statement is not completed. When using Microsoft Jet 3.5, it is possible to have some of the records committed by an SQL DML statement while others are not. An example of this would be when the Microsoft Jet cache is exceeded. The data in the cache is written to disk and the next set of records is modified and placed in the cache. Therefore, if the connection is terminated, it is possible that some of the records were saved to disk, but others were not. This is the same behavior as using DAO looping routines to update data without an explicit transaction in Microsoft Jet 3.0. If you want to avoid this behavior, you need to add explicit transactions around the SQL DML statement to define a set of work and you must sacrifice the performance gains.