BACK UPS - Setting Archive bit set to 0

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Daniel Slick

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Jul 12, 2015, 5:28:45 PM7/12/15
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All:
I came across this question in the quiz engine:

An incremental backup process
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Can anybody explain better what the archive bit being set to Zero means?  I understand Full, Differential, Incremental back ups but not getting what is meant by setting archive bit to 0. 


CCCure Support

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Jul 12, 2015, 5:34:50 PM7/12/15
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Good day to all,

Here is a quick description:
Whenever a file is created or changed, the operating system activates the Archive Bit or modified bit.

It simply tells your backup program whether or not the file has ever been backup up since it was created or last modified.

See a nice post at:
https://support.symantec.com/en_US/article.HOWTO22710.html

Also see:

The archive bit is a file attribute that is set whenever a file is modified. For backups that use archive bits, this bit is turned off after the backup completes, indicating to the system that the file has been backed up. If the file is changed again before the next backup, the bit will be turned on and Genie Backup Manager will back up the file.

Whenever a file is created or changed, the operating system activates the Archive Bit or modified bit . By default, unless you specifically select to use the archive bit, Genie Backup Manager uses the last modified date and time stamp to determine whether a file has been backed up.

Using the archive bit in determining changed files, however, can cause confusion if the user is not careful, if the data selection for more than one backup job overlap. To explain this, consider this scenario: Jack has two backup jobs that he has scheduled to run consecutively, named Documents and Work . The folder Monthly Reports was selected to be backed up by both backup jobs. Come backup time, the job Documents, will backup the folder the turn off the archive bit. When its time for the job Work to run, it will find that the folder has already been backed up and skips the folder.

When the archive bit method is used with full, increment or mirror backup, GBM will turn off the archive bit after each backup run. However, when used with differential backup, GBM will only reset the bit in the first full backup, but not in subsequent differential runs, this way, GBM will always keep backing up files that have changed since the first full backup.

http://www.genie9.com/support/manuals/gbmpro/sett_archive.htm


Best regards

Clement



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Daniel Slick

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Jul 12, 2015, 6:50:45 PM7/12/15
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Thank you Clement!  That's a good article. 
So also there really is no difference between incremental and differential back ups other than incremental using the setting the archive bit to Zero approach?  Differential uses last modified time stamp to know what's changed.

CCCure Support

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Jul 12, 2015, 6:58:55 PM7/12/15
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Good day Daniel,

Differential backups does not reset the archive bit, so the backup gets bigger daily since the last time the file was backup.

Incremental will reset the archive bit indicating the file was backup.

So let's say you do a full backup on Sunday.

The first incremental or differential you run on monday night would be exactly the same.

However, when you run a backup on Tuesday night,  the incremental would be only 24 hours of files but the differential would be 48 hours of files that were created or modified.

Best regards

Clement



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