Evil twin problem and subtractive merge
Could anyone explain what is a Evil Twin and Subtractive merge in Clearcase?
Answer
Evil Twin
An Evil Twin is an element that you have removed (using rmname) and want to re-add, but it's 'evil twin' exists in previous versions of the directory.
You have to remember that each element had a unique ID, so you are attempting to add an element with the same name - but with a different UID. This is not allowed.
The best way to deal with an Evil Twin is to relink the newest version you can find of the existing element to the new version of the directory. You can then make a new version of the element and replace the data within it.
Subtractive Merge
A subtractive merge is the opposite of a selective merge.
A selective merge (the default, bog standard merge) adds the changes from another element version into your checked-out version.
A subtractive merge attempts to remove the changes made in a different version from the version you have checked out - because it's a bad version, you've made mistakes in it etc.