Symptoms

This article provides information about leap second and its influence on OSA products.

Leap seconds are a mechanism to adjust for differences between time as kept by atomic clocks and the notion of time based on solar days and years which is more intuitive, but less accurate due to astronomical phenomena such as the earth's rotation speed slowing down due to tidal friction.

Cause

The next leap second insertion is scheduled for June 30th, 2015 at 23:59:60 UTC.

The sequence of dates of the UTC second markers will be: 

                      2015 June 30,     23h 59m 59s
                      2015 June 30,     23h 59m 60s
                      2015 July  1,      0h  0m  0s

Resolution

OSA customer services using Windows operating systems are not affected and will see no changes during the leap second. OSA customer services using RHEL and RHEL-based Linux distributions will be not affected by a leap second if they take into account two points :

  1. NTP time synchronization should be enabled on all servers in the infrastructure. On NTP-enabled servers leap second will be counted automatically. For systems where NTP synchronization cannot be enabled, please refer to workaround at the end of the article.

  2. Version of Linux distribution. According to appropriate Red Hat article system crash may occur on a receiving message about leap second. To avoid this, ensure that you are running RHEL 4.8, 5.4 or 6.2 and above. Please, consider updating you Linux installations before June 30th.

When both of these conditions are met, leap second will be counted seamlessly and will not lead to any services unavailability.

Possible side-effects for statistics gathering with OSA services:

  1. Statistical data which is calculated during the minute with the leap second will not contain information about the events which occurred during the leap second (for Windows systems);

  2. Statistical data which is calculated during the minute with the leap second will contain double information about the events which occurred during the leap second (for Linux systems).

More information about leap second handling and possible workarounds:

https://access.redhat.com/articles/15145

https://bugzilla.redhat.com/show_bug.cgi?id=479765

https://www.suse.com/support/kb/doc.php?id=7016150

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