White Paper: CM-Bridge using Clearcase UCM

Abstract

The purpose of this document is to consider the implications of connecting and synchronising a ClearCase UCM Vob with a subversion repository by using the Clearvision tool CM-Bridge (©Clearvision) which integrates two separate Software Configuration Management systems.

Prerequisites

Over the course of this document technical references will be made to the software in scope for discussion, the reader should have basic user knowledge of:

• IBM Rational ClearCase
• ClearCase UCM methodology and terminology
• Subversion (open source)

Introduction

The Aim of this case study is to determine the behaviour of bridging a ClearCase Vob using the UCM layer with a specified Subversion Repository.

In order to test these concepts a small UCM vob will be used. The vob will feature an integration stream as well as two development streams in a single project. Figure 1.0 shows the ClearCase version tree of the vob in question.

Figure 1.0

As you can see the vob contains labels, activities, integrations and a rebase. As it is small, there should be no issues in migrating the vob.

The vob also contains several unused components and a second unused project, these are in place as control objects to ensure the UCM objects bridge correctly.

Results

Preparing ClearCase

There are a number of recommendations when using CM-Bridge that become more important when using a UCM Vob.

CM-Bridge can be used with any stream, either a development or integration stream. It is crucial however to ensure the bridge has its own view, for the purpose of this study the following values were used:

Bridge views: - BRIDGE_DEV_VIEW, BRIDGE_INT_VIEW

Editable views :- DEV_VIEW, INT_VIEW

The bridge views will also require a dedicated activity (which must be set), the values used for this study were BRIDGE_ACTIVITY_DEV and BRIDGE_ACTIVITY_INT.

The integration streams delivery permissions were tested with various values, the default value (DISALLOWED) was used for all settings and proven to work, however various other configurations were used and none appeared to interfere with the activities of the bridge.

Starting the Bridge

The bridge can be started with or without an initial synchronisation between ClearCase and Subversion. This setting is entirely optional and completely compatible with a UCM Vob.

Output

The results from running the bridge were entirely as expected proving the tool to be compatible with ClearCase UCM.

All files from ClearCase were bridged into the subversion repository with subsequent updates represented in a new branch, additionally all files from subversion were successfully copied into the vob as long as the project that the view belongs to allows writing to the components in question.

Read Only ClearCase Components

It is notable that projects in ClearCase can contain components from other projects in a read only state. This feature, controlled in ClearCase does not migrate to Subversion.

Permissions must be set separately in subversion to maintain control of the repository. By default all branches are accessible, and editable by anyone with access to the repository. It is worth considering however that the TEST_PROJECT, originally containing only one single component in an editable state, now contains four. It is also important to note that any changes made to these components will not be copied back to ClearCase, attempting such will provide errors preventing the bridge from making any further updates to ClearCase.