Synthetic backups may unexpectedly fail to be scheduled. This can lead to data loss if older full backups expire and no newer synthetic backups have been taken. (Updated December 1, 2009)


Synthetic backups may unexpectedly fail to be scheduled. This can lead to data loss if older full backups expire and no newer synthetic backups have been taken. (Updated December 1, 2009)


Due to a scheduling issue in the NetBackup Policy Execution Manager (nbpem), synthetic full backups may fail to be scheduled and are skipped.  Other schedules ("traditional" full and incremental) will continue to run, but new synthetic full backups are never scheduled and continue being skipped until a traditional full backup is run followed by an incremental backup.  This may correct itself with normal scheduling, subject to the policy schedule configuration, or by manual intervention from the administrator by running a full backup.

If the traditional full backups in a synthetic backup policy are set with a retention value shorter than the time between full backups, a data loss condition (gap) will be experienced when the expected synthetic full backup is unavailable for restore.

What is Affected:
The following versions of NetBackup may be affected if synthetic policies are enabled:
  • NetBackup 6.5.3 through 6.5.4
How to Determine if Affected:
Synthetic backup attempts which are expected to have run do not appear in the Activity Monitor.

If all full backups from a given policy should expire, incremental backups running as fulls may be seen in the Activity Monitor.  These would appear as incremental backups, but with an elapsed time and size comparable to a full backup.

Output from the following nbpemreq command can reveal this condition:
# nbpemreq -subsystems screen 1

nbpemreq can be found at the following paths:

For UNIX/Linux: /usr/openv/netbackup/bin/admincmd

For Windows: <install_path>\VERITAS\NetBackup\bin\admincmd

The output will show that the synthetic schedule is not scheduled for a future run due to "no incrementals found:"
07/16/09 07:55:48.595 [nbpemreq ] Weekly_Synth::1: Ignored, no incrementals for synthetic

However, this is incorrect.  This excerpt from the same nbpemreq command output shows that incrementals HAVE run... and are continuing to be scheduled:
07/16/09 07:55:48.599  [nbpemreq ]       Schedule: Weekly_Synth::1
07/16/09 07:55:48.599  [nbpemreq ]         Retention level: 2
07/16/09 07:55:48.599  [nbpemreq ]         Backup type: ST_FULL (0)
07/16/09 07:55:48.599  [nbpemreq ]         Frequency schedule (3 0:00:00 (259200))
07/16/09 07:55:48.599  [nbpemreq ]           Last backup data as of: 2009/07/15 23:24:09 (1242426249)
07/16/09 07:55:48.599  [nbpemreq ]           Number of files: 13
07/16/09 07:55:48.599  [nbpemreq ]           Image size: 2620038
07/16/09 07:55:48.599  [nbpemreq ]           Estimate size: 1048015
07/16/09 07:55:48.599  [nbpemreq ]           Snap time: 0:00:00 (0)
07/16/09 07:55:48.599  [nbpemreq ]           Last backup: 2009/07/01 19:01:27 (1246492887)
07/16/09 07:55:48.599  [nbpemreq ]           Run time: 2009/07/09 09:14:58 (1247148898)
07/16/09 07:55:48.599  [nbpemreq ]           Last dumplevel: 0
07/16/09 07:55:48.601  [nbpemreq ]       Schedule: Daily_Incr::1
07/16/09 07:55:48.601  [nbpemreq ]         Retention level: 2
07/16/09 07:55:48.601  [nbpemreq ]         Backup type: ST_INCR (1)
07/16/09 07:55:48.601  [nbpemreq ]         Frequency schedule (14:00:00 (50400))
07/16/09 07:55:48.601  [nbpemreq ]           Last backup data as of: 2009/07/15 23:24:09 (1247718249)
07/16/09 07:55:48.601  [nbpemreq ]           Number of files: 13
07/16/09 07:55:48.601  [nbpemreq ]           Image size: 873346
07/16/09 07:55:48.601  [nbpemreq ]           Estimate size: 1048015
07/16/09 07:55:48.601  [nbpemreq ]           Snap time: 0:00:00 (0)
07/16/09 07:55:48.601  [nbpemreq ]           Last backup: 2009/07/15 19:00:58 (1247702458)
07/16/09 07:55:48.602  [nbpemreq ]           Run time: 2009/07/15 19:00:58 (1247702458)
07/16/09 07:55:48.602  [nbpemreq ]           Last dumplevel: 0

Note: In the examples above, Weekly_Synth and Daily_Incr are schedule names for the synthetic full and incremental schedules.  The number following the schedule name is the stream number - multistreamed policies will have similar output for every stream for each schedule in the policy and an entry for the parent job with a "stream number" of -1.

In addition, running an nbpemreq -predict_all command may fail to return a prediction for the next run using the synthetic schedule of the policy.

Formal Resolution:
The formal resolution to this issue (Etrack 1728027) is included in the following release:
  • NetBackup 6.5 Release Update 5 (6.5.5)
NetBackup 6.5.5 is available at the following link:

Increasing the retention value of traditional full backups ensures that data remains available for restore, even if synthetic full backups are not available.

If applying the NetBackup 6.5.5 release update is not feasible at this time, a fix for this issue has been posted for NetBackup 6.5.4.  To obtain a replacement nbpem binary, click on the link below (or in the "Related Documents" section) to obtain TechFile 331593:

If this issue is experienced and both applying the 6.5.5 release update AND the above workarounds are not feasible, please contact Symantec technical support, referencing this TechNote ID and Etrack 1728017 to obtain a replacement nbpem binary for NetBackup 6.5.3 or

Best Practices:
Symantec strongly recommends the following best practices:
1. Always perform a full backup prior to and after any changes to your environment.
2. Always make sure that your environment is running the latest version and patch level.
3. Perform periodic "test" restores.
4. Subscribe to technical articles.

How to Subscribe to Email Notification:

Article Subscription:
Subscribe to this TechNote for any updates that are made to this article, by clicking on the following link:

Software Alerts:
If you have not received this from the Symantec Technical Support Email Notification Service, please click on the following link to subscribe to future Notifications:

Terms of use for this information are found in Legal Notices.



Did this article answer your question or resolve your issue?


Did this article save you the trouble of contacting technical support?


How can we make this article more helpful?

Email Address (Optional)