if (returnDbHandle(db) == 0) {
if ((db != null) && (returnDbHandle(db) == 0)) {
    synchronized void releaseDbHandle(isc_db_handle db) throws GDSException {        if (returnDbHandle(db) == 0) {            dbHandleUsage.remove(db);            freeDbHandles.remove(db);            gds.isc_detach_database(db);        }    }