When it comes to DB performance, the best solutions are extremely dependend from the DB system you are using. I can give you some hints how to optimize your case for MS Access, for MS SQL server you will probably need a completely different approach.

1. For single user access, keep the database file locally

If you want to keep your db file on a network drive for nightly server backups, but don't have the requirement to access the database by a second user at the same time, just copy it over from a network folder before the processing starts, do the processing and copy it back afterwards. That releases your program from any network overhead.

2. Do not use ADO.DB. Use classic ADO or DAO!

Why? ADO and DAO can be up to 20 times faster for batch read & update scenarios on Access than ADO.DB, due to the additional abstraction overhead. That is at least what I have measured when creating such kind of applications. Moreover, these older APIs contain the concept of a recordset (which works similar to the concept of a cursor in other SQL databases), but is AFAIK not supported by ADO.DB. Recordset will allow you to navigate to a certain record, read it, modify it and write it back within the same connection and "transaction" (whatever the latter means in MS Access).

Some general hints

As a general rule of thumb, which is also valid for different databases: for your kind of scenario, the more lightweight the storage is, the faster your program can be. The fastest approach is often what you can do in-memory, the second fastest are flat files, then come lightweight DB solutions like MS Access or SQLite, and finally (often slower by an order of magnitude) heavy-weight client/server databases with full transaction management.

Of course, this is only a very rough guideline - the final performance you get will depend on the gory details of your implementation, and the available hardware & network.

When it comes to DB performance, the best solutions are extremely dependend from the DB system you are using. I can give you some hints how to optimize your case for MS Access, for MS SQL server you will probably need a completely different approach.

1. For single user access, keep the database file locally

If you want to keep your db file on a network drive for nightly server backups, but don't have the requirement to access the database by a second user at the same time, just copy it over from a network folder before the processing starts, do the processing and copy it back afterwards. That releases your program from any network overhead.

2. Do not use ADO.DB. Use classic ADO or DAO!

This may sound very old school and outdated, but ADO and DAO (which are fully available in VB.NET as COM components on every modern Windows system) can be up to 20 times faster for batch read & update scenarios on Access than ADO.DB, due to the additional abstraction overhead. That is at least what I have measured when creating such kind of applications. Moreover, these older APIs contain the concept of a recordset (which works similar to the concept of a cursor in other SQL databases), but is AFAIK not supported by ADO.DB. Recordset will allow you to navigate to a certain record, read it, modify it and write it back within the same connection and "transaction" (whatever the latter means in MS Access).

Some general hints (besides the usual "measure where your real bottleneck is"):

As a general rule of thumb, which is also valid for different databases: for your kind of scenario, the more lightweight the storage is, the faster your program can be. The fastest approach is often what you can do in-memory, the second fastest are flat files, then come lightweight DB solutions like MS Access or SQLite, and finally (often slower by an order of magnitude) heavy-weight client/server databases with full transaction management.

Of course, this is only a very rough guideline - the final performance you get will depend on the gory details of your implementation, and the available hardware & network.