Rational ClearCase - A quick start tutorial

If you have prior understanding of other version control systems , but has joined a new team that uses clearcase - here is a quick start for the SCM engineers in ClearCase

Concepts

• VOB or Versioned Object Base: This is the permanent data repository of a development tree or subtree storing all file system elements. It is typically hosted on in the network on a remote host and mounted as an MVFS file system on the user’s machine.
• View: A view is what you use to access a VOB transparently. Without a view, the VOB appears to be empty.
• Elements,Branches,and Versions: A versioned file system object in a VOB is called an element. There can be multiple versions of each element logically organized into a hierarchical version tree containing multiple branches/sub-branches.
• Config Spec: A config spec is a document that contains a set of rules that is used by the view for selecting the versions of elements. A simplified explanation would be that a config spec is a filter that determines what versions of elements from the vob gets loaded into a view. Typically the Clearcase admin or project lead will provide you with a config spec and it looks somewhat like this:

########################################
# config spec:
# line1 - Select any files I have checked out
# line 2 - Ignore lost+found.
# line 3 - Select the LATEST element on the main branch
########################################
element       *      CHECKEDOUT
element      …/lost+found/…      -none
element      *     /main/LATEST

Of course, a real config spec is much larger and more complicated.

Read More..

Usage

• So to get started, get your vob tag from your clearcase admin and activate your vob. Note: You may not need to perform this step as this process may have already been completed when your clearcase client installation was completed. Also note that you will need cleartool (ct) in your path.

  ct mount vob_tag

• Then create a view (say my_view) specifying where you want your view storage location.

  ct mkview -tag my_view /path/to/location/the_view.vws

• Now set the config spec.

  ct setcs your_config_spec

• You are now ready to check out your file.

  ct co -c ‘add your comment here’ <filename>

• After you have modified the file, you can check it in using the following command:

  ct ci -nc <filename>

  Use the -nc option if you do not want to add any comments.

Other common commands:

• Undo checkout:

  ct unco <filename>

• Check out a file but dont reserve it

  ct co -unres <filename>

• List all files checked out:

  ct lsco -all -cview

• Diff a file with its previous version

  ct diff -pred <filename>

• See the history of a file

  ct lshist <filename>