Export existing database from HSQLDB to Microsoft SQL Server

We are using Openfire 4.0.2 at work on a 64-bit Windows Server and our embedded HSQLDB database is getting huge; the openfire.script database is 345MB in size. I would like to export our database if possible to SQL Server 2016 Express. But the database is so huge I could not even look at the database without using the Java heap size parameters, like so:

java -Xms1024m -Xmx1024m -cp hsqldb.jar org.hsqldb.util.DatabaseManager

But the Dump option (and anything else under Tools) gives me a Java class not defined error, so I have no idea how to dump anything to a file. Even if I could do that, I do not know how to switch from an embedded database to an external one, or if that is even possible? I do not want to lose chat history, and I believe one of the reasons the database has grown so large is because I have the option to store offline messages, which I do not want to turn off and lose anything.

Hello. Why have I not received any kind of response?

Why have I not received any kind of response?

Because this is a volunteers only driven community and there are not many volunteers, they don’t have much time to solve issues and probably not many had such issue/scenario.

Oh, I see. Thank you.