Mode for partial incremental backup?

[ldmwndletsm]

According to the IBM document:

https://www.ibm.com/support/knowled....reference/r_cmd_copygroup_backup_define.html

MODE is used only during a full incremental backup. What then can a partial incremental capture? Only new files?

" MODE Specifies whether IBM Spectrum Protect backs up a file only if the file has changed since the last backup, or whenever a client requests a backup. This parameter is optional. The default value is MODIFIED. Possible values are: MODifiedSpecifies that IBM Spectrum Protect backs up the file only if it has changed since the last backup. IBM Spectrum Protect considers a file changed if any of the following is true:

• The date last modified is different
• The file size is different
• The file owner is different
• The file permissions are different

ABSoluteSpecifies that IBM Spectrum Protect backs up the file regardless of whether it has been modified.
The MODE value is used only for full incremental backup. This value is ignored during partial incremental backup or selective backup."

 

[marclant]

What then can a partial incremental capture? Only new files?

New and modified files just like a full incremental.

 

[ldmwndletsm]

How does that not contradict where IBM says: "The MODE value is used only for full incremental backup. This value is ignored during partial incremental backup or selective backup." ?

Is this a subtlety like all towns in Nevada are in the US but not the converse?

Perhaps, they're simply saying that TSM consults both the frequency and the MODE when performing a full incremental backup, and the file must satisfy both whereas with a partial incremental, it's able to determine this through some other means? If so, what means does it use to determine if the file is to be backed up if it's not checking the MODE? Maybe it's patently obvious?

 

[ldmwndletsm]

Okay, *MAYBE* they're saying that if it's a new file, natch, but if the file (path) already exists in its database then it backs it up *if and only if* it's been modified since the previous incremental (full or partial), BUT this might introduce the possibility that the file could have an older date in which case it might slip through and not get captured until another full incremental has been run? That possible? In other words, if you changed the content of a file, but kept the size the same, and you reset the modtime to a year ago, would the partial pass it up as not having been changed since the previous incremental of any kind?

OR are they instead saying that because a partial doesn't look at MODE (one value of which can be Absolute), a partial could not back up a file that has not changed as it could if it checked that setting; MODE=absolute).

Regardless, it would seem that a partial incremental is a subset of a full in terms of what it checks to determine whether or not to back up the file. Therefore, what is it not checking that a full does check other than MODE=Absolute? That's not clear to me.

 

[marclant]

I think you are over analyzing this. It just says that it ignores MODE if you do a partial incremental. It's still an incremental, it will still backup files that are new or modified within the file specification given in the command.

 

[ldmwndletsm]

Well, okay then. I think the documentation should be clearer on that, or at least have a statement to such, but documentation shortcomings in general could be belabored ad infinitum, with this one being far below the summit.

Anyway, it's pretty clear that 'Absolute' is not going to work since it doesn't pay attention to MODE, but I'm not concerned about that one. Any idea if frequency is affected?

 

[marclant]

I have not use frequency, I have not found a good valid use case for it. Might only apply if you are low on storage and only want clients to run backups every X number of days.

Most customers also don't use absolute either, not too many good use cases for it.

Leaving the default for both offers you much more flexibility. If you have a requirement for some clients to backup only every X number of days, associate them with a schedule that only runs every X number of days. If you have a requirement to backup all files on a client regardless if they changed, use a SELECTIVE instead of an INCREMENTAL, either in a schedule or manually.

 

[ldmwndletsm]

Okay, thanks much, Marclant. We have frequency set to 0, and MODE set to Modified. Good point about the schedule solution to an otherwise increased frequency and/or use of selective. Appreciate the feedback.