I've updated the downloads page to show the most recent versions:

• Firebird Server for Windows 1.5.3
• Firebird Embedded for Windows 1.5.3
• Firebird Server for Windows 2 RC1
• Firebird Embedded for Windows 2 RC1
• Firebird ADO.NET Provider 1.7.1 for .NET Framework 1.1
• FirebirdClient 2 RC3 for .NET Framework 2.0
  

A nice white paper by Roman Rokytskyy that describes the multi version concurrency control system used in Firebird in comparison to IBM DB2 and Oracle 9i.

So how does it work? The main idea was already presented when we talked about MS Word opening a file in read-only mode, but there are some important details. As the name implies, each record in the system might have multiple versions visible to different transactions. When a transaction modifies a record, a new version is written to the database, and a previous version, representing only the difference between the version of the record that was read by the transaction and the new value of the record, is written as a back version of that record.

http://www.firebirdsql.org/doc/whitepapers/fb_vs_ibm_vs_oracle.htm

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