VistaDB vs. Microsoft SQL Server 2008, ORACLE and DB2
VistaDB is not designed to be an replacement to Microsoft SQL Server, ORACLE or DB2. These high-performance enterprise level databases were designed for supporting large enterprise-wide database applications.
SQL Server is generally too expensive for most developers and small businesses. Even the entry level edition of SQL Server 2008 Standard costs approximately $1,849 per server for a 5 client access edition, which makes it cost prohibitive for most small to midsize companies that need to deploy multiple copies of their .NET applications. A single processor version of SQL Server 2008 costs $5,999 and may not be used on internet facing servers.
SQL Server also cannot be installed on Windows Server Web Edition due to licensing restrictions. VistaDB can install and run on Windows Server Web Edition (32 and 64 bit editions) without any deployment costs or restrictions.
In summary, SQL Server is overkill in size, features and cost for most developers and companies developing small to midsize database applications. A typical installation is well over 900 MB and consumes 500+ MB of RAM. These enterprise-level database systems are so complex that they usually need full-time Database Administrators (DBAs) to manage them.
For developers that need to build small applications for individuals or for departments within the organizations VistaDB can be a great alternative to these enterprise level databases since VistaDB does not require a system administrator, local machine administrator access, and deployment is a breeze. Consider using VistaDB as a complement to your smaller SQL Server, ORACLE or DB2 projects.
VistaDB as a local SQL Server caching database
Sometimes using VistaDB as a local cache for a larger remote database makes great sense to offload the server. Especially when running over a WAN link, or for remote workers who need offline access to the data.
ADO.NET Data Services Offline
Microsoft has announceed ADO.NET Data Services Offline (formerly called Astoria Offline) you will be able to use an Entity Framework model pointing to a local repository that the application always uses for database operations. The Entity Framework and Sync providers will then take care of syncing the local database to the remote SQL Server. This allows for offline use of VistaDB and cordinated updates back to SQL Server.