IBM DevOps Code ClearCase
| Company type | Software |
|---|---|
| Industry | Software configuration management |
| Founded | 1992 |
| Founder | Atria Software |
Area served | Medium to large-scale enterprises |
| Owner | IBM |
IBM DevOps Code ClearCase—also referred to as IBM Rational ClearCase—is a collection of software utilities designed to facilitate software configuration management (SCM) for source code and various development resources. It additionally oversees electronic design information, supporting the joint development of hardware and software components. Created by IBM, ClearCase acts as a key configuration management platform suitable for medium to large-scale enterprises, capable of managing projects involving hundreds or even thousands of contributors.
ClearCase accommodates two primary SCM approaches: UCM (Unified Change Management), which provides a ready-to-use framework, and base ClearCase, which delivers the fundamental infrastructure underlying UCM. Both configurations can be tailored to fit the specific requirements of different organizations.
Engineered for high scalability, ClearCase efficiently manages extensive binary files, large numbers of files, and voluminous repositories. Its functionalities include branching, labeling, and versioning directories, all designed to streamline the accurate merging of modified files. The platform enables process automation and enforcement through mechanisms such as triggers, attributes, hyperlinks, and metadata.
At the heart of ClearCase lies the MultiVersion File System (MVFS), a virtual file system that dynamically controls access to multiple file versions within workspaces. MVFS supports dynamic views across LANs and automatic views over both LAN and WAN networks.
ClearCase also delivers authoritative build auditing that produces metadata for each build output—documenting the build environment and providing a comprehensive bill of materials with precise file versions. This feature is essential for generating Software Bill of Materials (SBOM) and plays a vital role in ensuring compliance within regulated sectors. An integrated 'make' utility operates alongside build auditing to guarantee build integrity without depending on timestamps while enabling seamless sharing of build outputs between workspaces.
History
Initially developed by Atria Software, ClearCase was launched in 1992 for Unix platforms and subsequently made available on Windows. Some members of the Atria team had previously contributed to DSEE (Domain Software Engineering Environment) at Apollo Computer. Following Hewlett-Packard’s acquisition of Apollo in 1989, these developers departed to establish Atria. In 1996, Atria merged with Pure Software to form PureAtria, which was acquired by Rational Software in 1997. Subsequently, Rational was purchased by IBM in 2003. IBM has continued the development and marketing of ClearCase since then. In September 2016, IBM announced a strategic collaboration with HCL Technologies aimed at accelerating ClearCase’s evolution.
Infrastructure
ClearCase relies on the RDM Embedded database system provided by Raima, where each database instance is termed a VOB (Versioned Object Base). Database maintenance requires specialized expertise using Raima’s tools and often involves dedicated database administrators.
A crucial component is the Atria Location Broker Daemon (ALBD), which facilitates communication over LANs among connected machines. Starting with version 7, ClearCase servers operate on Websphere Application Server, with the Change Management Server (CM Server) managing client interactions via HTTP. The CM Server was later succeeded by the ClearCase Remote Client Wide-Area Network Server (CCRC WAN server), which continues to be based on Websphere technology.
Views
ClearCase utilizes its proprietary MultiVersion File System (MVFS) to mount VOBs as a virtual file system through dynamic views, facilitating consistent version selection and the generation of derived objects. This method supports early artifact handling prior to check-in, contrasting with conventional repository-and-sandbox workflows.
Snapshot views create local copies of repository content stored on the user's machine, allowing offline access. When reconnected, these views synchronize with the VOB, functioning similarly to CVS systems.
The ClearCase local client (CCLC) accommodates both dynamic and snapshot views, whereas the ClearCase remote client (CCRC) provides automatic and web views—both based on copy mechanisms. Automatic views utilize MVFS to maintain local, shareable pools of VOB objects.
From the user's perspective, a ClearCase view operates like a typical file system. Files generated inside a view remain "view-private" until explicitly added to source control, enabling isolated builds and facilitating collaborative workflows.
It is common for developers to manage several views simultaneously but share branches rather than individual views. Branch structures support project organization: a main development branch for the project at large, team-specific sub-branches, and personal branches for individual developers. Stable modifications made on branches are merged upward into parent branches.
The configuration specification
In base ClearCase, each view is governed by its configuration specification or config spec, which consists of a set of rules stored as a text file and compiled prior to use. These rules dictate which versions of elements (files or directories) are visible within that view. ClearCase evaluates the config spec sequentially, applying the first rule that matches. Config specs may incorporate other config specs through 'include' directives.
Within the UCM framework, config specs are automatically generated and managed by ClearCase UCM processes, removing the need for manual editing.
Builds
The MVFS network filesystem facilitates build auditing by tracking file input/output during builds and linking these activities to the commands that triggered them. This process generates a bill-of-materials known as a Configuration Record (CR), which enhances traceability for software configuration management and broader lifecycle management efforts. Build auditing is performed using tools such as clearmake, omake, or clearaudit (which can call Unix make).
The Versioned Object Base (VOB) retains all versions of files and directories alongside derived objects and their associated metadata.
A Configuration Record encompasses:
- The build procedure: the script or makefile that initiated the build
- Inputs: all files involved in the build along with their exact versions
- Outputs: all derived objects produced during the build
Dependency information contained within the CR enables the creation of views displaying every file accessed during the build and supports labeling those files and their specific versions.
MVFS allows sharing of derived objects ("winking in") among dynamic views when they share identical configuration records. These shared derived objects reside on the VOB server rather than within individual views, requiring builds to be conducted using clearmake or omake.
Dynamic views often exhibit slower performance compared to local file systems due to continuous server interactions; however, ClearCase’s make replacement tool helps reduce build times by avoiding unnecessary rebuilds. Ultimately, overall performance is significantly influenced by server capabilities.
Client types
Originally, ClearCase supported only full-featured ("fat") clients on Unix and Windows platforms. The release of version 7 brought the ClearCase Remote Client (CCRC), which is Eclipse-based and offered as a standalone Eclipse package, an Eclipse plugin, and extensions for other environments such as Visual Studio.
| Client | Network connection type | Repository connection | View types | User interfaces |
|---|---|---|---|---|
| ClearCase local client (CCLC) | Limited to LAN | RPC access to versioned object base (VOB) | Dynamic, snapshot | ClearTeam Explorer (GUI), cleartool (CLI) |
| ClearCase remote client (CCRC) | Supports WAN and LAN | HTTP(S) connection to VOB through CCRC WAN server | Automatic, web-based | ClearTeam Explorer (GUI), rcleartool (CLI) |
Integrations
ClearCase seamlessly connects with Rational Software tools such as ClearQuest and Rational Team Concert. Additionally, it integrates with Microsoft Visual Studio, Cadence Virtuoso, and the Eclipse IDE through dedicated plugins, thereby streamlining development processes.
Database replication
The ClearCase MultiSite feature enables teams spread across different locations to collaborate on synchronized replicas of the same VOB. These replicas can be synchronized using various configurations—one-to-one, ring, one-to-many, or many-to-many—with data transfer occurring unidirectionally or bidirectionally over any communication protocol.
DSEE
The Domain Software Engineering Environment (DSEE) introduced foundational concepts later incorporated into ClearCase. Its Apollo Domain file system allowed transparent replacement of files with their versioned counterparts during access. DSEE managed software modules and dependencies through a manually curated file list, facilitating efficient builds by reusing matching module versions.
DSEE originated the idea of a "version spec" or "thread," which is an ordered list of file versions used within user environments or build processes. These threads contained reserved copies, latest revisions, branched versions, labeled files, and versions associated with particular builds or releases. Version selection for development or bug fixes was governed by processing these threads from top to bottom on a per-file basis.
In the absence of Apollo’s file redirection mechanism, ClearCase employs the MultiVersion File System (MVFS) virtual file system. The thread concept corresponds with ClearCase’s dynamic views, while support for derived objects similarly reflects DSEE’s methodology.
Releases
V11.0.0 (March 2024) along with subsequent maintenance updates.
V10.0.1 (October 2023) including following fix packs.
V10.0.0 (December 2022) plus later maintenance releases.
V9.1.0 (December 2020) with subsequent patches.
V9.0.2 (January 2020) including following updates.
V9.0.1 (June 2017) along with later fixes.
V9.0 (March 2016) plus subsequent patches.
V8.0.1 (June 2013) including later fixes.
V8.0 (October 2011) with subsequent updates.
See also
References