Beside information about machines and their restore points, Veeam Backup Catalog keeps information for every backup job session. Session indexing data describe what machine restore points are related to a specific backup job session and what sets of files are required to restore a machine to a specific point in time.
Session indexing files vary for incremental and reversed incremental backup chains.
For incremental backup chains, a session indexing file contains information about only one restore point — the restore point that is created with this backup job session. Additionally, it contains information about a set of files that is required to restore a machine to this point in time. For example, if a backup chain contains 5 restore points, the 5th session indexing file will contain information about the 5th restore point and a group of 5 files that are required to restore the machine to this point in time.
BackupServer=BACKUP01
JobName=srv04
SessionDateUtc=05/13/2014 08:05:57.081
####################################################
# OIBS
oib0.VmName=srv04
oib0.BackupTimeUtc=05/13/2014 08:02:04.988
oib0.OibUID=f81f790c-103e-4351-81a4-e4ec8a8c290c
oib0.Platform=EVmware
oib0.Group=grp0
####################################################
# BACKUP FILE GROUPS
grp0.file0.Server=BACKUP01
grp0.file0.Path=c:\backup\srv04\srv042014-05-13T010101.vib
grp0.file0.ModifyDateUtc=05/13/2014 08:04:10.293
grp0.file1.Server=BACKUP01
grp0.file1.Path=c:\backup\srv04\srv042014-05-13T004536.vib
grp0.file1.ModifyDateUtc=05/13/2014 07:47:52.077
grp0.file2.Server=BACKUP01
grp0.file2.Path=c:\backup\srv04\srv042014-05-13T000053.vib
grp0.file2.ModifyDateUtc=05/13/2014 07:04:24.38
grp0.file3.Server=BACKUP01
grp0.file3.Path=c:\backup\srv04\srv042014-05-12T230102.vib
grp0.file3.ModifyDateUtc=05/13/2014 06:04:25.003
grp0.file4.Server=BACKUP01
grp0.file4.Path=c:\backup\srv04\srv042014-05-12T220051.vib
grp0.file4.ModifyDateUtc=05/13/2014 05:03:53.817
grp0.file5.Server=BACKUP01
grp0.file5.Path=c:\backup\srv04\srv042014-05-12T210105.vbk
grp0.file5.ModifyDateUtc=05/13/2014 04:07:55.047
For reversed incremental backup chains, a session indexing file contains information about all restore points engaged in the backup job session. In a reversed incremental chain, the last restore point is always a full backup. To produce a full backup and calculate incremental changes, Veeam Backup & Replication needs to address all points in the job. For this reason, the session indexing files refers not only to the restore point created with the backup job session, but also to all restore points preceding it.
Additionally, a session indexing file describes groups of files that are required to restore a machine to all possible restore points. For every restore point, there is a separate group of files.
For example, if you have a reversed incremental chain of 3 restore points, the session indexing file for the last backup job session will contain information about 3 restore points and will describe three groups of files:
- Group 0 will list restore points that are required to restore the machine to the 1st, the earliest restore point
- Group 1 will list restore points that are required to restore the machine to the 2nd restore point
- Group 2 will list restore points that are required to restore the machine to the 3rd, the latest restore point
BackupServer=SRV02
JobName=srv01_reversed
SessionDateUtc=05/14/2014 11:20:18.952
####################################################
# OIBS
oib0.VmName=srv01
oib0.BackupTimeUtc=05/14/2014 10:56:55.993
oib0.OibUID=47c62e82-3066-478c-8272-1fb65a47d601
oib0.Platform=EVmware
oib0.Group=grp1
oib1.VmName=srv01
oib1.BackupTimeUtc=05/14/2014 11:02:20.15
oib1.OibUID=d39f4a3c-2b5b-415a-ae0d-e9acc49f63a0
oib1.Platform=EVmware
oib1.Group=grp2
oib2.VmName=srv01
oib2.BackupTimeUtc=05/14/2014 11:16:52.779
oib2.OibUID=1f3c31bf-9541-46ac-9826-62ecfd76a291
oib2.Platform=EVmware
oib2.Group=grp3
####################################################
# BACKUP FILE GROUPS
grp0.file0.Server=BACKUP
grp0.file0.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T035606.vrb
grp0.file0.ModifyDateUtc=05/14/2014 10:56:55.993
grp0.file1.Server=BACKUP
grp0.file1.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T040137.vrb
grp0.file1.ModifyDateUtc=05/14/2014 11:18:14.43
grp0.file2.Server=BACKUP
grp0.file2.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T041612.vbk
grp0.file2.ModifyDateUtc=05/14/2014 11:18:45.973
grp1.file0.Server=BACKUP
grp1.file0.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T040137.vrb
grp1.file0.ModifyDateUtc=05/14/2014 11:18:14.43
grp1.file1.Server=BACKUP
grp1.file1.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T041612.vbk
grp1.file1.ModifyDateUtc=05/14/2014 11:18:45.973
grp2.file0.Server=BACKUP
grp2.file0.Path=c:\backup\srv01_reversed\srv01_reversed2014-05-14T041612.vbk
grp2.file0.ModifyDateUtc=05/14/2014 11:18:45.973
BSessionVersion=5
A full backup file “moves forward” with every new backup job run, and Veeam Backup & Replication updates groups of files, correspondingly. This helps maintain valid groups of files required to restore a machine to a necessary point in time.
The session indexing files maintain groups of files for all restore points that have ever existed in the backup chain. This behavior lets you search and restore machine guest OS files in archived backups.
When a backup is archived to tape or to a secondary backup repository, you can still browse the machine file system to this point in time using historical indexing data. Once you find a necessary file, Veeam Backup Enterprise Manager uses the session indexing file to inform you what group of files is required to restore the machine to the selected point in time.
