An explanation of the "Overwrite Protection Period" and the "Append Period"

Article:TECH5459  |  Created: 1998-01-13  |  Updated: 2014-04-11  |  Article URL http://www.symantec.com/docs/TECH5459
Article Type
Technical Solution

Product(s)

Issue



How does Backup Exec manage media and data retention?


Error



This is a general information document regarding Media Management.

For an overview of some of the core basics of the Overwrite Protection Period and Append Period in Backup Exec, see this video:


Solution




Overwrite protection period:

Overwrite protection period is the amount of time specified in hours, days, weeks, or years to keep a piece of media from being overwritten. While the default Overwrite protection period for a media set is Infinite - Don't Allow Overwrite, the Overwrite protection period for the media set can be changed by the user. If the Overwrite protection period is set to four weeks for example, the media will be protected from being overwritten for four weeks. After the four weeks are over, the media becomes "recyclable" and can be overwritten. The Overwrite protection period starts at the end of each job run, not the beginning. It is lengthened each time a media is modified.

Append Period:

Append period is the amount of time specified in hours, days, weeks, or years, that data may be added (appended) to media. While the default Append period for a media set is Infinite - Allow Append, the Append period for the media set can be changed by the user. If the Append period is set to four weeks for example, the media can be appended to for the next four weeks. After the four weeks are over, the media can no longer be appended to. Appending jobs will add to the Overwrite protection period; append adheres to the first job run on tape. The Append period starts at the time that a media is first allocated to a media set.

The overwrite and append periods can be configured from the Media tab within Backup Exec. Highlight and right-click on any media set name and select Properties (Figure 1).

Figure 1


Scratch media:

Media that can be overwritten by any backup operation is in the Scratch Media set. Scratch media can either be new media, blank media, erased media, or media moved from another media set and will be displayed in blue under the Scratch Media set. Scratch media cannot be appended to. If Scratch media is used for a backup operation, Backup Exec automatically moves the media to the User Media set that was targeted during the backup operation. The media color will then change from blue to black, and the media will inherit the overwrite protection period and append periods for that User Media set.


Retired media:

Media that has been discarded and will never be used by Backup Exec for any media operation, unless the media is moved manually out of the media set. If a media becomes defective, the user should place the defective media into the Retired Media set. Users can also place media in the Retired Media set to protect the media from being overwritten. This action is required when the media overwrite protection level is set to None (see important note on media overwrite protection level).


Imported media:

Media created by another installation of Backup Exec for Windows or many other backup products will be treated as Imported media.

Note:

1. When using either the Backup Exec overwrite protection level of None or Partial, a backup operation will overwrite Imported media if no available Scratch or Recyclable media is found in the drive. Both the None and the Partial overwrite protection levels can be configured to prompt the user before overwriting Imported media.
2. To append to Imported media, the media must be manually moved to the User Media set targeted in the backup operation before the backup operation occurs.


User Media sets:

User Media sets contain all the allocated media that are assigned to media sets.


Allocated media:

Media that is part of a User Media set and has not had its overwrite protection period expire. The media may also be available for append operations if the append period for the media has not expired. The media will be displayed in black under the User Media set. Once the overwrite protection period expires, the Allocated media becomes Recyclable media and will remain in the User Media set.


Recyclable media:

Allocated media that is part of a User Media set and has had its overwrite protection period expire. The media is available for overwrite operations or append operations (append operations are only possible if the append period still allows the media to be appended to). The media will be displayed in blue under the User Media set.

How does Backup Exec choose media to overwrite (Figure 2)?

Figure2

  1. Overwrite scratch media before overwriting recyclable media contained in the targeted media set

  2. Backup Exec will overwrite scratch media first before overwriting recyclable media when an overwrite job occurs. If there is no scratch media in any of the storage devices, Backup Exec overwrites recyclable media in the targeted media set. If there is no recyclable media found, Backup Exec automatically searches for other media to overwrite. Which media is overwritten depends on the level of overwrite protection (Full, Partial, or None) that has been set. If this option is selected, more media may be required for the same number of jobs as compared to when it has been chosen to overwrite recyclable media first. Because this option affects the order in which Backup Exec overwrites media, choosing to overwrite scratch media first may allow the recyclable media to be preserved longer for possible recovery.

  3. Overwrite recyclable media contained in the targeted media set before overwriting scratch media

  4. Backup Exec will overwrite recyclable media in the targeted media set before overwriting scratch media when an overwrite job occurs. If there is no recyclable media in any of the storage devices, Backup Exec overwrites scratch media. If no recyclable or scratch media are found, Backup Exec automatically searches for media to overwrite. Which media is overwritten depends on the level of overwrite protection that has been set (Full, Partial or None). If it has been chosen to overwrite recyclable media in the targeted media set first, the same media will be reused more frequently as compared to when it has been chosen to overwrite scratch media first.

When performing an overwrite backup operation while Backup Exec is set to use scratch media before recyclable media, Backup Exec follows these steps to find media available for overwrite:

  1. Backup Exec first searches the Scratch Media set for media that can be overwritten. If using an autoloader and more than one scratch media is available for the backup operation, Backup Exec will select the scratch media that has a lower allocation date or time.

  2. Allocation time can be seen from the Devices tab (Figure 3).
    Figure 3


    Allocation date or time is changed by an overwrite or an erase job on the media.

  3. If scratch media is not available for overwrite operations, Backup Exec next searches for recyclable media in the User Media set targeted in the backup operation. Backup Exec will select the media based on the number of hours the media has been recyclable (media that have been recyclable will be chosen before media that has just turned recyclable). If two recyclable media have been recyclable for the same number of hours, Backup Exec will then select the recyclable media based on the lowest allocation date or time.

  4. If recyclable media from the User Media set targeted in the backup operation is not available for overwrite operations, Backup Exec next searches for recyclable media in the all other User Media sets for media that can be overwritten. If more than one recyclable media is available for the backup operation, Backup Exec will select the media based on the number of hours the media has been recyclable (media that have been recyclable will be chosen before media that has just turned recyclable). If two recyclable media have been recyclable for the same number of hours, Backup Exec will then select the recyclable media based on the lowest allocation date or time.

  5. If recyclable media is not available for overwrite operations and Backup Exec Media overwrite protection has been configured as Full, Backup Exec will prompt for a scratch media.

  6. If recyclable media is not available for overwrite operations and Backup Exec Media overwrite protection has been configured as Partial or None, Backup Exec will search for media that can be overwritten in the Imported Media set. If using an autoloader and more than one Imported media is available for the backup operation, Backup Exec will select the Imported media based on the lowest allocation date or time.

  7. If Imported media is not available for overwrite and Backup Exec Media overwrite protection has been configured as Partial, Backup Exec will prompt for a Scratch media.

  8. If Imported Media is not available for overwrite and Backup Exec Media overwrite protection has been configured as None, Backup Exec will search for Allocated media (media in User Media sets that is not recyclable). If using an autoloader and more than one allocated media is available for the backup operation, Backup Exec will select the Allocated media based on the lowest allocation date or time.

  9. If Backup Exec still cannot find media, Backup Exec will prompt the user for scratch media (Figure 4).

  10. Figure 4



When performing an overwrite backup operation while Backup Exec is set to use recyclable media before scratch media, Backup Exec follows these steps to find media available for overwrite:

  1. Backup Exec first searches for recyclable media in the User Media set targeted in the backup operation. If using an autoloader and more than one recyclable media is available for the backup operation, Backup Exec will select the media based on the number of hours the media has been recyclable (media that have been recyclable will be chosen before media that has just turned recyclable). If two recyclable media have been recyclable for the same number of hours, Backup Exec will then select the recyclable media based on the lowest allocation date or time.

  2. If recyclable media in the targeted User Media set is not available, Backup Exec next searches for Scratch media that can be overwritten. If using an autoloader and more than one scratch media is available for the backup operation, Backup Exec will select the scratch media based on the lowest allocation date or time.

  3. If scratch media is not available for overwrite operations, Backup Exec next searches for recyclable media in all other User Media sets for media that can be overwritten. If more than one recyclable media is available for the backup operation, Backup Exec will select the media based on the number of hours the media has been recyclable (media that have been recyclable will be chosen before media that has just turned recyclable). If two recyclable media have been recyclable for the same number of hours, Backup Exec will then select the recyclable media based on the lowest allocation date or time.

  4. If recyclable media is not available for overwrite operations and Backup Exec Media overwrite protection has been configured as Full, Backup Exec will prompt for a scratch media.

  5. If recyclable media is not available for overwrite operations and Backup Exec Media overwrite protection has been configured as Partial or None, Backup Exec will search for media that can be overwritten in the Imported Media set. If using an autoloader and more than one Imported media is available for the backup operation, Backup Exec will select the Imported media based on the lowest allocation date or time.

  6. If Imported media is not available for overwrite and Backup Exec Media overwrite protection has been configured as Partial, Backup Exec will prompt for a Scratch media.

  7. If Imported media is not available for overwrite and Backup Exec Media overwrite protection has been configured as None, Backup Exec will search for Allocated media (media in User media sets that is not recyclable). If using an autoloader and more than one allocated media is available for the backup operation, Backup Exec will select the allocated media based on the lowest allocation date or time.

  8. If Backup Exec still cannot find media, Backup Exec will prompt the user for scratch media (Figure 5).

  9. Figure 5



How does Backup Exec choose media to append?
Backup Exec now allows the user to choose what Backup Exec should do when performing an append job but no appendable media is present. This can be done on a per job basis. The two new options are:

  1. Append to media, overwrite if no appendable media is available

  2. Backup Exec will append the backup to the media set listed in the Destination | Media Set field in this dialog box. The backup set is appended if an appendable media is available in the selected media set; if not, an overwritable media is used and added to the media set.

  3. Append to media, terminate if no appendable

  4. Backup Exec will append the backup to the media set listed in the Destination | Media Set field in this dialog box. The backup set is appended if an appendable media is available in the selected media set; if not, the job is terminated.

    Caution: If any job fills a media, the job will only continue on another piece of overwritable media. Backup Exec will not append to multiple media in the same job. Depending on your configuration, overwritable media is selected from scratch media or recyclable media. If the media in the drive is not overwritable, a message is displayed, which requests for a scratch media to be inserted.


When performing an append backup operation and the backup job is set to append to media, overwrite if no appendable media is available, Backup Exec follows these steps to find available media:

  1. Backup Exec first searches for appendable media in the User Media set targeted in the backup operation. If no appendable media can be found and the backup job is configured to Append to media, overwrite if no appendable media is available, Backup Exec changes the backup operation from append to overwrite and continues with the search for media.
  2. Note: Refer to items 1 to 8 of the When performing an overwrite backup... section

  3. If the job is able to find appendable media, the job will mount the media and proceed to write the job to that media. If the backup job needs more media to complete the backup operation, any further requests for media to complete the operation will be for media that is able to be overwritten as Backup Exec cannot append to more than one media on the same job.

When performing an append backup operation and the backup job is set to append to media, never overwrite, Backup Exec follows these steps to find available media:

  1. Backup Exec first searches for appendable media in the User Media set targeted in the backup operation.

  2. If no appendable media can be found, the backup job is terminated.

  3. Caution: It is strongly recommended that careful consideration should be made before setting the media overwrite protection level to None. When the overwrite protection level is set to None, all media is subject to being overwritten regardless of media set, overwrite protection period, append period, or any other property.



Legacy ID



192265


Article URL http://www.symantec.com/docs/TECH5459


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