75 ways to demystify DB2: #11: Tech Tip : What is the impact of leap second on DB2

Body

Hello!

I am happy because I am going to get one more second to work on my PMRs! How? Leap Second!
 

So what is a leap second?

This is a definition from Wikipedia:

A leap second is a one-second adjustment that is occasionally applied to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time. Without such a correction, time reckoned by Earth's rotation drifts away from atomic time because of irregularities in the Earth's rate of rotation. Since this system of correction was implemented in 1972, 25 such leap seconds have been inserted. The most recent one happened on June 30, 2012 at 23:59:60 UTC.[1] A leap second will again be inserted at the end of June 30, 2015 at 23:59:60 UTC.[2]

How will it affect DB2?

Currently, DB2 is configured to read its timestamp from the Operating System where DB2 is installed. You may want to check with your OS administrator to find out how the Operating System is going to handle leap second.

Some useful information:

Leap Second on RedHat Linux: https://access.redhat.com/articles/15145
Gist of it is that for RedHat systems running Network Time Protocol (NTP), they will show 23:59:59 twice as the leap second is inserted. For RedHat systems not running NTP, they will not insert that extra second, and time will just roll over from UTC 23:59:59 to 00:00:00 without inserting an extra second. Those non-NTP systems will then be 1 second ahead/faster, and the clocks will need to be adjusted.

More information on NTP and leap second can be found here: http://www.ntp.org/ntpfaq/NTP-s-algo-real.htm

On AIX, if NTP is present, the system clock will stay at 23:59:59 for an extra second before rolling over to 00:00:00 otherwise it will move from 23:59:59 to 00:00:00 without inserting an extra second.

Hope you will utilize an extra second in your life to read this blog :)

Thanks,
-Swati Thorve