[perforce] What is the difference between "Rollback..." and "Back Out Submitted Changelist #####" in Perforce P4V

I want to reverse the changes from one of my checkins. In the right-click context menu of the particular changelist, there are these two options:

• Rollback...
• Back Out Submitted Changelist

What is the difference between these two? In what situations should I use either one?

Backout restores or undoes our changes. The way it does this is that, P4 undoes the changes in a changelist (default or new) on our local workspace. We then have to submit/commit this backedout changelist as we do other changeslists. The second part is important here, as it doesn't automatically backout the changelist on the server, we have to submit the backedout changelist (which makes sense after you do it, but i was initially assuming it does that automatically).

As pointed by others, Rollback has greater powers - It can restore changes to a specific date, changelist or a revision#

Reverse a changelist submission

You cannot undo a successful changelist submission, but you can reverse previously submitted changes in two ways:

Rollback restores a file or set of files back to a specified changelist, date or revision. Any changes made after that point in time are not retained. Back out removes specific changes made at a given changelist, date or revision but allows a user to keep changes made in subsequent revisions.

For details please refer to https://www.perforce.com/perforce/r13.1/manuals/p4v/Working_with_changelists.html

At its simplest, the difference is one of plurality:

• Backout backs out of a single changelist (whether the most recent or not). i.e. it undoes a single changelist.
• Rollback rolls back changes as much as it needs to in order to get to a previous changelist. i.e. it undoes multiple changelists.

I used to forget which one is which and end up having to look it up many times. To fix this problem, imagine rolling back as several rotations then hopefully the fact that rollback is plural will help you (and me!) remember which one is which. Backout sounds 'less plural' than rollback to me. Imagine backing out of a single parking space.

So, the mnemonic is:

• Rollback → multiple rotations
• Backout → back out of a single car parking space

I hope this helps!

I explain this to users by comparing Perforce changelists to a stack (from data structures).

Backing out removes one item from anywhere in the stack.

Rolling back removes n items from the top of the stack.

Rollback... will prompt you to select a folder to rollback, ie, it will work on specific folders, and you can rollback to labels or changlists or dates. Back out works on the files in specific changelists.