There are many architectural differences between Microsoft® Access and Microsoft SQL Server™. Access is designed to handle a relatively small number of users accessing a relatively small amount of data. SQL Server is designed to handle anything from the smallest desktop database to the largest enterprise situation. SQL Server supports a greater number of features than Access supports.
Before you begin the migration process, familiarize yourself with SQL Server so you are prepared to reconcile the differences between it and Access.
Current backups of your data are always important, but they are essential when you make changes to your database. The migrating process does not delete any data; however, you can expect to delete the local Access tables in the .mdb file after the process is complete and has been tested. Also, you may need to consult a working copy of your original Access application in the future.
The size of your database will not change significantly when it is transferred to SQL Server. It might be smaller than your Access .mdb file because you are moving the tables only, not forms, reports, or Microsoft Visual Basic® for Application modules.