ClearCase

ClearCase is a software configuration management (SCM) system designed to manage source code and other artifacts across development teams. It originated with Atria Software and, after acquisitions, became part of IBM’s Rational product line. ClearCase supports centralized and distributed workflows through a client-server architecture that stores versioned data in Versioned Object Bases (VOBs).

A VOB is the repository that contains versions of files and directories along with metadata. Access to VOBs is provided to users through views, which come in two main forms: dynamic views, which mount a MultiVersion File System (MVFS) and present versions of files as a live filesystem, and snapshot views, which copy selected files to a local workspace for editing. Common operations include checkout and checkin, branching and merging, labeling, and creating baselines for release tracking.

ClearCase also offers Unified Change Management (UCM), a methodology that uses streams and activities to organize work and coordinate baselines across teams. File histories and access are preserved across sites with ClearCase MultiSite replication, enabling distributed development with synchronized repositories.

The tool runs on multiple platforms, including Unix, Linux, and Windows, and provides integrations with development environments and IDEs such as Eclipse and Visual Studio. ClearCase is widely used in large enterprises and regulated environments where rigorous configuration management and traceability are required, though it is often cited for its complexity and licensing costs.

Alternatives include Git, Subversion, Perforce, and Plastic SCM.