Which non SQL Database ?

[Dave]

Interesting thread. It started as a discussion of small footprint, embeddable non-SQL databases and has ranged all over the place. 

For the original purpose of this thread, it certainly sounds like SQLite fits the bill. It's a great package. If you need SQLite's ease of use and simplicity, but you're looking for multi-threaded concurrent access and replication for High Availability, then I would suggest Berkeley DB. It's completely compatible wit SQLite's SQL API, but provides better concurrency and scalability, as well has HA. 

If you're looking for a non-SQL solution, Berkeley DB offers several non-SQL APIs, including the original BDB key/value pair API, a Java Collections API and a POJO-style Java API (called the Data Persistence Layer). 

Disclaimer: I'm one of the product managers for Berkeley DB, so I'm a little biased. :-) But I was amused to see claims that BDB wasn't concurrent (not true) or that there were products which were "BDB-like" (why not use the real thing?) so I thought that I would chime in. Good luck on your search. 

Regards, 

Dave