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Delayed Stubbing

Delayed stubbing prevents data loss in the event that you must perform a disaster recovery (DR) restore. Without delayed stubbing, when you perform a DR restore, recalls might fail for files that were backed up after the DR backup that is selected to be restored. By delaying stubbing, you can roll back to a previous CommServe DR version (within the minimum DR backups setting) without any data loss.

Stubbing is delayed by the number of DR backups plus the number of days that must pass after a DR backup. By default, this is set to three (3) DR backups + two (2) days.

Delayed stubbing is disabled on a client when the agent is installed initially and remains disabled until seven (7) days after the first backup job is run on the client. After those seven days have passed, delayed stubbing automatically becomes enabled using the default value of three DR backups plus two days. The default value is the minimum recommended value for effective data loss prevention. However, you can change the number of DR backups and the number of days to delay the stubbing process by configuring the nMinDRBackupBeforeStubbing (DR backups) and nMinDaysBeforeStubbing (days passed) additional settings at the CommServe level.

About This Task

Consider the following when you use synthetic full backups:

  • Synthetic full backup jobs must be run less frequently than the DR backup jobs.
  • Retention of the DR backup job must be longer than the frequency of the synthetic full backup job schedule.
  • The time interval between the synthetic full backup jobs must be greater than the maximum value of (m*x, n).

    where m and n are nMinDRBackupBeforeStubbing and nMinDaysBeforeStubbing additional setting values respectively, and x is the DR backup frequency in days.

  • Each time a synthetic full backup job is run, the count for the number of DR backups and the number of days to delay the stubbing process is reset to additional setting values. If the additional settings are not present on the CommServe computer, then the count for the number of DR backups and the number of days to delay the stubbing process is reset to the default values of three and two respectively.

Notes:

  • If the nMinDRBackupBeforeStubbing additional setting is not present (null) at the CommServe level, then stubbing is delayed by three DR backups.
  • If the nMinDaysBeforeStubbing additional setting is not present (null) at the CommServe level, then stubbing is delayed by two days.
  • Both the additional settings are required for delayed stubbing. To disable delayed stubbing, set the value of both additional settings to 0.

Procedure

Modify the number of DR backups to run before the stubbing process:

  1. From the CommCell Console, right-click the CommServe, and then click Properties.

    The CommCell Properties dialog box appears.

  2. Click the Additional Settings tab.
  3. Click Add.

    The Add Additional Settings dialog box appears.

  4. In the Name box, type nMinDRBackupBeforeStubbing.
  5. In the Value box, type the number_of_DR_backups_to_delay_stubbing_after_backup.
  6. Click OK.

Modify the number of days to delay the stubbing process:

  1. From the CommCell Console, right-click the CommServe, and then click Properties.

    The CommCell Properties dialog box appears.

  2. Click the Additional Settings tab.
  3. Click Add.

    The Add Additional Settings dialog box appears.

  4. In the Name box, type nMinDaysBeforeStubbing.
  5. In the Value box, type the number_of_days_to_delay_stubbing_after_backup.
  6. Click OK.

Example

To delay the stubbing process for 7 DR backups and 3 days, configure the settings as follows:

  • nMinDRBackupBeforeStubbing = 7
  • nMinDaysBeforeStubbing = 3

The delayed stubbing process involves two steps:

  1. Find a DR backup that meets the requirement of 3 days, and greater than or equal to the 7th DR backup (counting from the latest DR job to the oldest DR job).
  2. Any file that is backed up before the start time of the DR backup determined in the previous step will become eligible for stubbing.