Because SQL Server 7.0 introduces a new on-disk format, the upgrade is different from earlier upgrades (for example, from SQL Server version 6.0 to SQL Server version 6.5). However, the SQL Server Upgrade Wizard makes upgrading from SQL Server 6.0 or SQL Server 6.5 to SQL Server 7.0 a simple operation.
The SQL Server Upgrade Wizard is designed with a typical user in mind. Usually, most users can go through the SQL Server Upgrade Wizard, accept the default values and options, and complete a successful upgrade to SQL Server 7.0. Even so, you should prepare for and understand the upgrade process and what the SQL Server Upgrade Wizard can do for you.
The SQL Server Upgrade is built on some fundamental assumptions. The wizard is designed to upgrade all the databases in a single pass. The purpose of the SQL Server Upgrade Wizard is to upgrade a single instance of SQL Server 6.x to a single instance of SQL Server 7.0 in a single pass. You can run multiple upgrades (for example, one database at a time) as long as they use the same SQL Server 6.x installation; however, this is not recommended because cross-database dependencies cannot be resolved if you upgrade only one database at a time. You cannot run SQL Server 6.x and SQL Server 7.0 on one computer simultaneously.
After you upgrade to SQL Server 7.0, there is no correlation, data mapping, or data sharing with an earlier installation of SQL Server 6.x. If you choose not to delete the SQL Server 6.x data files, you have two full copies of the data on disk: one for the SQL Server 6.x installation and one for the SQL Server 7.0 installation. When you are satisfied with the upgrade, use the custom uninstaller for SQL Server 6.x on the Microsoft SQL Server-Switch menu to delete the SQL Server 6.x data files. You may also want to plan a test-run of an upgrade to determine if there is any reason to prepare a fallback plan.