connect to db2 udb on zlinux from cics/vse

In a Natural pseudoconversational cics session, we have to reconnect to db2 every time a screen i/o (like INPUT USING MAP) is performed. This is very tedious. We try to use REFRESH=ON parameter in NDBPARM, but the connection is however lost after a screen i/o. Can someone help us to avoid to connect to db2 after every screen i/o?
Thanks in advance.