To prevent UCA from storing chat history on the server, there two commands. I'd suggest copying the command to the windows clipboard, and then pasting the command into putty by right-clicking on the putty window, rather than attempting to enter them manually.
(1) edit /etc/e-smith/templates/opt/intertel/conf/sip_ims.ini/50Configuration set EnableFile=no. (if you're familiar with linux you can use vi editor to do this as well, I had to do this as my version of linus didn't recognise the "edit" command)
(2) expand-template /opt/intertel/conf/sip_ims.ini
Next, to delete the existing chat history stored on the server:
(1) stop the SIPIMS service from the UCA diagnostic page. From Server Manager, go to the main UCA configuration page, then at the bottom of the page under "Diagnostics", press the "Perform Server Diagnostics" button. Look for "SIPIMS" and click the "Stop" link to the right.
(2) move all files from the /opt/intertel/data/imarchive directory, maybe move them to /root by doing a 'mv hab_ims_archive* /root' from the /opt/intertel/data/imarchive directory. You can do this with putty, but if there are lots of files, you may want to use an application like WinSCP so that you can create folders, and drag and drop multiple files at once. Or, you can delete them from the putty command line if you are comfortable doing so - and will not want to keep the history at all.
(3) restart the UCA server completely.