Hi,

> We are planning to build a mission-critical application for a financial services provider where integrity, better concurrency and guaranteed backup/recovery is a must. I want to know whether FireBird is suitable for very large databases where about 20,000 concurrent users will be using the database at about the same time.
>
> Where FireBird stands as compared to its open-source counterparts? Are there any case studies available for such large databases.

there is a paper in IBPhoenix's site :

http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_enterprise_firebird

Hope it helps ...

regards,