+--- 1.2.5 2011/05/06
+
+Filter z3950_client may be configured to always send a close APDU
+to backend target when connection/session is closed. This will only
+happen if close APDU is not already sent. Enabled by configuration
+for z3950_client (force_close).
+
+Filter virt_db and multi: relay close APDU.