Question: I am seeking a way to measure my
instance startup time and shutdown times so that I can make reports of system
uptime. Are there any views in the V$, AWR or ASH tables that gives us the
complete history regarding the startup and shutdown of databases.
Answer: Startup information is stored in v$instance.startup_time,
and uptime can be easily computed as sysdate - startup_time, but shutdown
data is problematic.
During a normal shutdown, Oracle writes message to the alert log, but under an
emergency abort (i.e. un-plug the server), nothing appears in the logs, nor
within Oracle. Oracle stops abruptly, and there is no way to see it, except
periodic daemon polling for a PMON or SMON process.
Startup and shutdown are written to the alert log, externally, but you could
define the alert log as an external table and then make a SQL query to parse
out the shutdown and startup messages.
Or, try this query to see uptime, from v$instance and compute the total uptime
for the database.
select
'Hostname : ' || host_name
,'Instance Name : ' || instance_name
,'Started At : ' || to_char(startup_time,'DD-MON-YYYY HH24:MI:SS')
stime
,'Uptime : ' || floor(sysdate - startup_time) || ' days(s) ' ||
trunc( 24*((sysdate-startup_time) -
trunc(sysdate-startup_time))) || ' hour(s) ' ||
mod(trunc(1440*((sysdate-startup_time) -
trunc(sysdate-startup_time))), 60) ||' minute(s) ' ||
mod(trunc(86400*((sysdate-startup_time) -
trunc(sysdate-startup_time))), 60) ||' seconds' uptime
from
sys.v_$instance;
If you assume that PMON startup time is the same as the database startup time,
you can get the uptime here:
select
to_char(logon_time,'DD/MM/YYYY HH24:MI:SS')
from
v$session
where
sid=1;
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