diff backup size like full

[guilhemlflo]

Hello, a diff backup of a shot is set to have the full backup size. he also appeared:

23 mai 2018 18:26:48 - Info bpbkar32 (pid=6568) Backup started

23 mai 2018 18:26:48 - Info bpbkar32 (pid=6568) change time comparison:<disabled>

23 mai 2018 18:26:48 - Info bpbkar32 (pid=6568) archive bit processing:<enabled>

which was not the case before.

No change a priori on the policy. there is no accelerator and backup by on a LTO4 mono tape drive 

would anyone have an idea? or how to modify these parameters?

Thanks

[Marianne]

When last did a Full backup run for this client and this policy?
Is the Full backup still valid (not expired)? 

Was anything changed in the backup policy since the last full backup (like Backup Selection) ? 

[guilhemlflo]

last full : 10 days, the backup is valide (i can restore some file of this backup)

and there is some diff with full size two days ago.

there no change in the policy. Backup selection is "all local drive"

[Marianne · Accepted solution]

You will need to check full bpbkar log on the client to see what's going on. 
I suggest logging level between 1 and 3. 

[Tape_Archived]

You also need to check if there were any changes from the OS side, please ask your Server Admin if they have done changes that may changed archive bit for all files on files system of the os??