By issuing following script you will extract exact uptime of database cum Hostname, Instance Name & Database Start time:

Syntax:
 column hostname format a26
 column “Instance Name” format a16
 column “Started At” format a26
 column “Database Uptime” format a52
 SELECT
 host_name as Hostname,
 instance_name as “Instance Name”,
 to_char(startup_time,’DD-MON-YYYY HH24:MI:SS’) as “Started_At”,
 floor(sysdate – startup_time) || ‘ days(s) ‘ ||
 trunc( 24*((sysdate-startup_time) -
 trunc(sysdate-startup_time))) || ‘ hour(s) ‘ ||
 mod(trunc(1440*((sysdate-startup_time) -
 trunc(sysdate-startup_time))), 60) ||’ minute(s) ‘ ||
 mod(trunc(86400*((sysdate-startup_time) -
 trunc(sysdate-startup_time))), 60) ||’ seconds’ as “Database_Uptime”
 FROM
 sys.v_$instance;

HOSTNAME

——–
Instance Name Started_At
——– —————
Database_Uptime
————————————–
localhost.localdomain
DemoDB 13-APR-2013 12:11:40
216 days(s) 22 hour(s) 1 minute(s) 52 seconds

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Note: Please don’t hesitate to revert in case of any query OR feedback.

Thanking you.

Have a easy life ahead.