If the True Image Restore information from the immediately previous backup has been pruned or compressed, subsequent synthetic backups complete with Status Code 0 (successful), but fail to capture all files for the backup.

Article:TECH44683  |  Created: 2005-01-08  |  Updated: 2005-01-08  |  Article URL http://www.symantec.com/docs/TECH44683
Article Type
Technical Solution

Product(s)

Environment

Issue



If the True Image Restore information from the immediately previous backup has been pruned or compressed, subsequent synthetic backups complete with Status Code 0 (successful), but fail to capture all files for the backup.

Solution



What is Affected:
This issue affects the following versions of NetBackup:
- VERITAS NetBackup (tm) Enterprise Server:  5.0, 5.0 MP1 through 5.0 MP5; 5.1, 5.1 MP1 through 5.1 MP3; and 6.0 GA
- VERITAS NetBackup (tm) Server:  5.0, 5.0 MP1 through 5.0 MP5; 5.1, 5.1 MP1 through 5.1 MP3; and 6.0 GA

Problem Description:
If for any reason during the Synthetic backup, bpdbm cannot read the required True Image Restore (TIR) records from any of the preceding backup images, the synthetic backup will not contain all the necessary files, but will complete successfully with a status code 0.  Shown below is a list of several possible reasons why the TIR information could not be read.
  • The image file from the immediately previous backup has been corrupted.
  • The image file from the immediately previous backup has been compressed (only on UNIX master servers).
  • The TIR information from the immediately previous backup has been pruned.  This is unlikely, as NetBackup does not prune the TIR information until after the synthetic backup completes successfully, but it is possible if the last full or synthetic backup was expired or deleted.

Symantec highly recommends performing regular "Full" backups of any clients which use a Synthetic backup schedule until the fix or the workaround for this issue can be implemented.  

How to Determine if Affected:
If the environment is running Synthetic backups, there are two ways to determine if the environment is affected.  The first option is preferred, as it does not require access to the client and eliminates any concerns about dynamic changes to the client's file system.  The second option provides a cursory review of the environment, but may not provide a complete picture.

Option 1
Convert the last regular normal incremental backup and synthetic full backup to ASCII using the cat_convert command and count the lines in the new ASCII .f files.  They should both contain the same number of lines.  If they do not, this indicates there is a problem.

To determine what .f files to convert to ASCII, do the following:
On a Windows master server, the .f files are found in the <install_path>\veritas\netbackup\db\images\<client_name> directory.
On a UNIX master server, the .f files are found in the /usr/openv/netbackup/db/images/<client_name> directory.
1. Convert the CTIME of the .f file name to human readable format by following the information in the related technote.
2. The synthetic backup's CTIME is one second different than the CTIME of the most recent incremental backup prior to the synthetic backup.  In the following example, the V_TEST_1125345399_FULL.f file is the synthetic backup, and the CTIME is one larger than the incremental shown.  

V_TEST_1125345398_INCR.f
V_TEST_1125345399_FULL.f

The cat_convert binary is found in: <install_path>\NetBackup\bin\  (It is in /usr/openv/netbackup/bin on a UNIX server)
3. Find the <image_name>.f file () associated with the two backups, and copy them to a temporary location, such as C:\temp or /tmp.
4. From a command prompt, issue the following command if running NetBackup 5.0 or 5.1:
cat_convert -b2a /tmp/<image_name>.f /tmp/<image_name>_ascii.f
5. From a command prompt, issue the following command if running NetBackup 6.0:
cat_convert -dump /tmp/<image_name>.f /tmp/<image_name>_ascii.f
This converts the file from binary to ASCII.  This output can be piped to wc -l (on a UNIX system) to count the number of lines.

Option 2
Check the size in kilobytes of the synthetic full backup in the image file.  It should be approximately the size of the backed up file system.  

The size of the backup can be checked using the bpimagelist command.  

# bpimagelist -U -client <client_name> -d <date>
Backed Up         Expires       Files       KB  C  Sched Type   Policy
----------------  ---------- -------- --------  -  ------------ ------------
11/21/2005 15:34  12/05/2005        5    81889  N  Differential synth
11/21/2005 15:29  12/05/2005        6   138536  N  Differential synth
11/21/2005 14:53  12/05/2005       88  4722792  N  Full Backup  synth

The size, shown in kilobytes (KB) indicates how much data was backed up by the policy.  

Formal Resolution:
This issue will be formally resolved in the following NetBackup maintenance packs:
  • VERITAS NetBackup Enterprise Server 5.0, Maintenance Pack 6 (MP6), recently released.
  • VERITAS NetBackup Enterprise Server 5.1, Maintenance Pack 4 (MP4), recently released.
Both 5.0 MP6 and 5.1 MP4 are now available at the following link:  http://support.veritas.com/menu_ddProduct_NBUESVR_view_DOWNLOAD.htm

  • VERITAS NetBackup Enterprise Server 6.0, Maintenance Pack 1 (MP1), currently scheduled for release in late December of 2005.
Once released, this maintenance pack will also be available at the following link:    http://support.veritas.com/menu_ddProduct_NBUESVR_view_DOWNLOAD.htm ,

After the appropriate maintenance pack, mentioned above, is applied to your environment, Symantec strongly recommends performing a "Full" backup.


In the event that one of the formal resolutions mentioned above cannot be applied immediately, please implement one of the workarounds from the next section in this document and perform a "Full" backup.

The NetBackup pack resolves the problem with synthetic backups, where if the TIR+ file entry information is not found the backup skipped the file and finished with a status 0, by changing the exit status code.  The backup now fails with the appropriate status code.  

Workaround
There are a few workarounds for this issue.  They are:
  • Disable synthetic backups by removing synthetic backup schedules from the policy.
  • Confirm the incremental or full images for this policy are not deleted or expired. (Ensure the frequency of the full backups meets disaster recovery time frames.)
  • Uncompress the image catalog for the client(s) using synthetic backups (only for UNIX master servers).  To uncompress client catalog information, perform the following steps:
1. Verify that the partition where the image catalog resides has enough space to uncompress the image records.
2. Stop the request daemon, bprd, by running:
/usr/openv/netbackup/bin/admincmd/bprdreq -terminate
3. Verify that bpdbm is running by using:
/usr/openv/netbackup/bin/bpps
4. Expand Host Properties > Master Servers. Open the properties of a host. On the Global Attributes properties page, clear the Compress Catalog Interval check box.
5. Set the Compress Catalog Interval Global Attributes property to 0.
6. Change to the /usr/openv/netbackup/bin/admincmd directory and run the following command on any clients utilizing synthetic backups:
bpimage -decompress -client <client_name>
7. Restart the request daemon, bprd, by running:
/usr/openv/netbackup/bin/initbprd

Additional References:
VERITAS NetBackup 5.0 System Administrators Guide for UNIX, Volume I, p. 152
VERITAS NetBackup 5.0 System Administrators Guide for Windows, Volume I, p. 152
VERITAS NetBackup 5.1 System Administrators Guide for UNIX, Volume I, p. 154
VERITAS NetBackup 5.1 System Administrators Guide for Windows, Volume I, p.153

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.

If you have not received this TechNote from the Symantec Email Notification Service as a Software Alerts, please subscribe at the following link:
 http://maillist.support.veritas.com/subscribe.asp







Supplemental Materials

SourceETrack
Value493268
DescriptionSynthetic backup should fail if TIR+ information not found for a file entry

SourceETrack
Value499607
DescriptionSynthetic backup should fail if TIR+ information not found for a file entry

SourceETrack
Value499608
DescriptionSynthetic backup should fail if TIR+ information not found for a file entry

SourceETrack
Value499610
DescriptionSynthetic backup should fail if TIR+ information not found for a file entry

SourceETrack
Value499611
DescriptionSynthetic backup should fail if TIR+ information not found for a file entry

SourceETrack
Value355414
DescriptionSynthetic Backup produces an image containing only the last incremental

SourceETrack
Value495409
DescriptionSynthetic backup will miss files if catalog compress interval is too small


Legacy ID



280022


Article URL http://www.symantec.com/docs/TECH44683


Terms of use for this information are found in Legal Notices