Problem with monitor the Oracle database with ODBC

[h.karimi]

Hi
I want to monitor Oracle database by Zabbix
I use ODBC and make a item with the type of "database monitor" to run my query for monitor the database

But when database is down or overload, it can`t able to make ODBC connection and the item status changes to "not support" and disable my trigger then disable the action to alert me

How can i make a trigger to check the Oracle database is down or overload?
Thanks