Explanation

The Oracle database process is monitored as Unknown when the following situation is observed:

The MonitorCommandScript for the Oracle database searches for the process ora_pmon_<Oracle_SID>. If this process is found, the script checks whether the database is open for requests using the following commands on the node where the state Unknown is monitored:

#su - <Oracle_user>
#sqlplus /nolog
#connect / as sysdba
#select status from v\\$instance;
#exit

If the select statement returns the status OPEN, the MonitorCommandScript returns the status Online, in which the database allows transactions.

Example output for status OPEN:

sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on Fri Feb 4 17:56:37 2011
Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> connect / as sysdba
Connected.
SQL> select status from v$instance;
STATUS
------------
OPEN

For any other state, for example STARTED, the MonitorCommandScript returns the status Unknown, since the database is neither Online nor Offline, but also not in an intermediate state like Starting or Stopping.

Example output for status STARTED:

sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on Fri Feb 4 17:53:39 2011
Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> connect / as sysdba
Connected.
SQL> select status from v$instance;
STATUS
------------
STARTED