The Chequered Career of nBackup
The incremental backup utility toolset nBackup is not a friendly beast. An operational misstep can break a database. Under load, in some conditions, it can be a database-killer without any human intervention, especially under Firebird v.2.1 or v.2.0.
There’s a proviso, though. A lot of the problem code was eliminated by a thorough revamp for Firebird 2.5. The threadability of attachments in v.2.5 is also thought to have reduced some of the instability of nBackup The improvements were not backported to the v.2.1 or 2.0 series because it was structurally infeasible.
This article is not a “How-to” for using nBackup. The Firebird Project documentation for proper use of this toolset is excellent and can be read or downloaded from the Documentation pages at the Firebird web site.