Firebird is a smaller database server. It's not designed for applications where there are hundreds of concurrent users, or where data entry rates are very high. It also lacks a "hot backup" facility that can run without undue impact on users.
However, many corporate databases are not very large in size, and in such situations an Oracle or a Sybase might be overkill. If you have a lot of data (Gigabytes) with only a few users, like a decision support system, or less data than that and only a score of users, then Firebird may suit you very well. It operates best when you build the hardware underneath it with RAID or kernel level redundancy in disk access. You want to do backups rarely, or else be able to do them overnight.
This was first published in April 2005