1.2 ClearCase Hosts

ClearCase is a distributed application with a client/server architecture. Any development task (for example, execution of a single ClearCase command) may involve programs and data on several hosts. Every host in a ClearCase network plays one or more of the following roles.

• Client host. Each ClearCase user works at a ClearCase client host, running programs such as cleartool, clearmake, and various ClearCase graphical user interfaces (GUIs), as well as other software (for example, development tools, a Rational Suite, and operating system utilities). ClearCase must be installed on each client host. A client installation can include the multiversion file system (MVFS), which provides support for dynamic views. If a client uses only snapshot views, it does not need the MVFS.

• Server host. Any host on which a VOB or view is created is a server host. Some hosts may be dedicated servers on which client software rarely used (and may not even be installed). Other server hosts double as clients. ClearCase must be installed on each server host.

• Registry server host. One host in the network acts as the ClearCase registry server host. Each host is assigned to a particular registry server host at ClearCase install time. This host stores access-path information for all the VOBs and views in the network. ClearCase client and server programs on all hosts communicate with the registry server host to determine the actual storage location of ClearCase data. You may also designate a backup registry server host that can assume the ClearCase registry server role if the primary registry server host fails.

• License server host. One or more hosts in the network act as license server hosts, authorizing and limiting ClearCase use according to the terms of your license agreement. Each host on which ClearCase is installed is assigned to a particular license server host and communicates with that host periodically.

• Networkwide release host. One host in the network acts as the networkwide release host. A directory on this host stores an entire ClearCase release that has been extracted from the distribution CD. When necessary, ClearCase patches can be applied to a release area to update the entire release with the latest enhancements and defect fixes. Certain installation options allow ClearCase hosts running UNIX to access ClearCase programs and data through symbolic links to the release area instead of having the programs and data installed on local storage. ClearCase hosts running Windows do not access the networkwide release host after installation is complete. The networkwide release host does not need to run ClearCase.

• ClearCase Web server host. If you want to use the ClearCase Web interface, you'll need at least one ClearCase Web server host. See Chapter 29, Configuring a Web Server for the ClearCase Web Interface, for more detail.

• Non-ClearCase UNIX hosts. ClearCase may not be installed on every host in your network. In fact, it is not possible to install it on hosts whose architectures ClearCase does not yet support. Such hosts cannot run ClearCase programs, but they can access ClearCase data, through standard UNIX network file system facilities. You administer these export (or share) mechanisms using standard UNIX tools.

• Network Attached Storage Devices. Certain Network Attached Storage (NAS) devices are supported for use with ClearCase. These devices can be used to store any ClearCase programs or data, including VOBs and views. NAS devices do not run ClearCase. They simply provide storage that ClearCase hosts access over the local area network. The Release Notes for Rational ClearCase and ClearCase MultiSite contain the most current information about supported NAS devices.