A transaction is already active

General
1

connectionPool = new SimpleJDBCConnectionPool(
“org.hsqldb.jdbc.JDBCDriver”,
“jdbc:hsqldb:mem:sqlcontainer”, “SA”, “”, 50, 100);

TableQuery q1 = new TableQuery(“domains”, connectionPool);
q1.setVersionColumn(“VERSION”);
domainsContainer = new SQLContainer(q1);

Object id = domainsContainer.addItem();
domainsContainer.getContainerProperty(id, “DOMAIN_NAME”).setValue(domainName);
domainsContainer.getContainerProperty(id, “CLIENT_NAME”).setValue(clientName);
domainsContainer.commit();

This is my setup for a SQLContainer. When I try to use multiple threads to insert data into the db I get for line “domainsContainer.commit();” the following error: java.lang.IllegalStateException: A transaction is already active!

As you can see I am using 50 initial connections to the DB and 100 max connections, so the problem should be in the SQLContainer.

What am I missing or do not understand?

All help is appreciated.