问题
Normally, the first committed version should start from 1. Version 0 is identical with branch point. But now I got a only version 0, and this prevent me to checkin any other version coz it warned me that the branch already created.
回答1:
As explained in "Before adding files and directories to source control", the version 0 is a placeholder marking the start for all versions in a given branch:
You can end up with only the version 0 when you undo-checkout a file you just checked out in a new branch (in that case, only a version 0 for the newly created branch remains).
Regarding branches, you can have error like "element already has a branch of type branch", but only when there is an issue with the server and client time (clock) being not in sync.
回答2:
ClearCase creates version 0 when you create an element (or a branch), which is usually checked out automatically. Version 0 is always either empty, or same as the branched version, as you noted. There shouldn't be any problem simply checking in version 1 on top of it.
Note that branches are created when you check out, not when you check in, so you shouldn't get any warnings on check-in. If you post the exact command line and warnings/errors, we'll probably be able to help you out more.
It could perhaps be that you've created a new element on your branch, and you're missing "/main/0 -mkbranch" in your config spec.
HTH.
来源：https://stackoverflow.com/questions/5309333/why-i-only-get-a-clearcase-version-0