It looks like hqqldb hasn’t been updated in openfire in a while. Openfire is using 1.8.0.x, which was last updated in 2008. hsqldb is currently at 2.3.3. There appears to be large list of improvements and fixes since 2008 It might be worth checking out.
HyperSQL Database Engine (HSQLDB) download | SourceForge.net
I welcome the idea of updating the backend, but with soo many changes (over 7 years) it may be difficult to fine tune for Openfire. Unless databases don’t change so drastically
[OF-955] Update HSQLDB to the latest version - Jive Software Open Source
Thanks wroot! I’ll prob try the updated engine at some point to see what happens.