NetBackup and leap years

Article:TECH156297  |  Created: 2011-03-23  |  Updated: 2012-02-03  |  Article URL http://www.symantec.com/docs/TECH156297
Article Type
Technical Solution

Product(s)

Issue



How does NetBackup handle leap years and leap centuries and is it “leap year compliant?”


Solution



NetBackup and PureDisk (including NetBackup appliances) use standard UTC time for operation including scheduling and setting of retention levels.  As such they remain aligned to UTC time in respect of time adjustments such as leap years and leap seconds and there is no requirement to make separate adjustments to any internal "NetBackup clock".

Job scheduling is unaffected by leap years as all job scheduling is either frequency (day/time) or calendar based.  Frequency based backups will run at the same frequency irrespective of calendar dates.  Jobs scheduled for particular times of day or on specific days of the week are also unaffected by leap years and are  fully "leap year compliant."

As backup jobs are scheduled by "start windows" rather than a specific times the exact start time of a backup varies slighty from day to day and leap second variations are absorbed by this slight drift. 

Retention periods may be affected by leap years and leap seconds, as NetBackup retention periods are calculated in seconds relative to the time a backup is created and retention periods are calculated on the basis of a 365 day (31536000 second) year.  Longer term retention backups (> 4 years) may expire earlier (one day per 4 year period) than expected.  This "drift" in expiration date is linked to the number of leap years occurring within the retention period.

When required, retention periods may be set to adjust for leap year days. Symantec recommends that customers who require backups to be retained for a specific minimum period that includes leap years should increase the retention period to account for the interim leap year days.  For example, if a ten year retention is required, the associated NetBackup retention period may be configured with a retention period of 3653 days, not 3650.  Retention periods can be adjusted in the master server properties in the Administration GUI.




Article URL http://www.symantec.com/docs/TECH156297


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