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Backup versions of files with time stamps prior to January 1970 or after February 2106 are subject to premature expiration

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Abstract

The IBM Spectrum Protect backup-archive client and the IBM Spectrum Protect for Space Management client can incorrectly store atime, mtime, or ctime time stamps of files on the IBM Spectrum Protect server if the time stamp is earlier than January 1, 1970 or later than February 7, 2106. This can lead to premature expiration of backup versions of an affected file. If an affected file is migrated, the subsequent backup or archive operation will prematurely recall the file data. If an affected file is restored or retrieved by the backup-archive client, or recreated by dsmmigundelete, then the affected time stamps in the file differ from the original time stamps.

Content

Problem description

When a file is backed up, archived, or migrated to the IBM Spectrum Protect server, undetectable data corruption of the file's atime, ctime, or mtime time stamp can occur in that stored copy if the time stamp is earlier than January 1, 1970 12:00:00 AM GMT, or later than February 7, 2106 6:28:15 AM GMT. This problem is documented in APAR IT28106.

Consequences of this problem include:

  • During incremental backup operations, affected files are always backed up, even if they have not changed. When the number of backup versions exceeds the VEREXISTS setting of the management class's backup copy group, then the oldest backup version expires. Thus if a file has not actually changed, but is backed up anyway, this behavior can lead to premature expiration of the file's backup versions.
  • When an affected file is restored or retrieved by the backup-archive client, or recreated by dsmmigundelete, then the affected time stamps differ from the original (correct) time stamp. Although a time stamp is not part of the file's content, certain applications might not function correctly if the time stamps are wrong. For example, IBM Spectrum Protect for Space Management and Tivoli Storage Manager for Space Management use the file's last access time (atime) to determine when files are eligible for migration to lower-tier storage. Incorrect time stamps can lead to either premature or delayed migration of data. The file content is not lost, but this is an example of how time stamp integrity can impact other operations or applications.

Required conditions for this problem to occur

The problem can occur for a given file when all of the following conditions are true:

  • The file resides on an AIX, Linux, or macOS file system that is not IBM Spectrum Scale ("GPFS"). Files on GPFS are not affected because GFPS does not support time stamps earlier than January 1, 1970 12:00:00 AM GMT, or later than February 7, 2106 6:28:15 AM GMT.
  • The file's atime, ctime, or mtime time stamp is earlier than January 1, 1970 12:00:00 AM GMT, or later than February 7, 2106 6:28:15 AM GMT.
  • The file is bound to a management class whose backup copy group is configured with a VEREXISTS value other than NOLIMIT. Premature expiration of backup cannot occur when VEREXISTS is set to NOLIMIT.

Levels affected

  • IBM Spectrum Protect Backup-Archive Client for UNIX and Linux (including macOS) versions 8.1.x
  • IBM Spectrum Protect for Space Management version 8.1.x
  • IBM Tivoli Storage Manager Backup-Archive Client for UNIX and Linux (including macOS) versions 7.1.x and earlier
  • IBM Tivoli Storage Manager for Space Management version 7.1.x and earlier
Note: IBM Tivoli Storage Manager versions earlier than 7.1 are at End of Service.

Immediate action

1. Check whether any files could be affected by this problem by scanning your non-GPFS file systems for files with atime, ctime, or mtime time stamps earlier than January 1, 1970 12:00:00 AM GMT, or later than February 7, 2106 6:28:15 AM GMT. One way to do this is:

  
a. Create two test files that have modification dates of December 31, 11:59:59 GMT and February 7, 2106 6:28:15 AM GMT, respectively. Note that the touch commands use the local time, and the following examples are based on a local time of GMT-05:00 hours (US Eastern Time):

touch -m -t 210602070128.15 it28106_max
touch -m -t 196912311859.59 it28106_min
  
b. Use the find command to identify files with affected atime, ctime, or mtime values:
find / ! -newer /it28106_min -or -newer /it28106_max -or ! -cnewer /it28106_min -or -cnewer /it28106_max -or ! -anewer /it28106_min -or -anewer /it28106_max


2. Use the touch command on each affected file to set the file's time stamps to the current time. Note: Before modifying the file's time stamps, check with the file owner to ensure it is alright to update the file's time stamps.

3. To prevent premature expiration of backup versions, change the VEREXISTS setting in the backup management class's copy group to NOLIMIT. Make a note of the original VEREXISTS value so that VEREXISTS can be set to its original value after the fix for this problem is installed.

Fix

Apply a fixing backup-archive client version when it is available. The problem is fixed in these product levels:

  • IBM Spectrum Protect Backup-Archive Client 8.1.8.0. Current target availability is June 2019.
  • IBM Tivoli Storage Manager Backup-Archive Client 7.1.8.6. Current target availability is July 2019.
IBM Tivoli Storage Manager versions earlier than 7.1 are at End of Service. Users of affected versions earlier than 7.1 are advised to upgrade to one of the above supported versions.

Note: Users of IBM Spectrum Protect for Space Management must apply the backup-archive client package that includes the space management feature.

After the fix has been applied, set the management class's backup copy group VEREXISTS value to its original value.

Related information

APAR IT28106

Cross reference information
Product Component Platform Version Edition
Tivoli Storage Manager Backup-Archive Client AIX, HP-UX, Linux, Mac OS, Solaris All Versions
IBM Spectrum Protect for Space Management AIX, Linux All Versions
Tivoli Storage Manager for Space Management AIX, Linux All Versions

Document information

More support for: IBM Spectrum Protect

Component: Backup-Archive Client

Software version: All Versions

Operating system(s): AIX, HP-UX, Linux, Mac OS, Solaris

Reference #: 0883238

Modified date: 07 June 2019