26.1 Network Regions

Ideally, your network's VOB and view storage directories are accessible at the same pathnames throughout the network. Figure 34 shows a simple network in which global naming has been achieved.

Figure 34 Network with Global Naming

Uniform global naming may not be achievable if your network supports both Windows and UNIX hosts, hosts with multiple network interfaces, or UNIX computers with multiple aliases.

ClearCase servers require consistent pathnames to shared storage areas. If you cannot achieve global consistency, you must partition your network into a set of network regions, each of which is a consistent naming domain. Each region has the following characteristics:

• Each ClearCase host must belong to a single network region.

• All hosts in a given network region must be able to access ClearCase physical data storage (that is, all VOB storage directories and the storage directories of shared views) using the same full pathnames.

• All hosts in a given network region must use the same locale setting if VOB-tags or view-tags use multibyte characters.

• Developers access VOBs and views through their VOB-tags and view-tags. All hosts in a given network region use the same tags.

• Each VOB must have a tag in the region of the host on which the VOB storage directory resides. Each view must have a tag in the region of the host on which the view storage directory resides. A VOB or view can have tags in other regions as well.

For example, a VOB and a view may be accessed in different network regions as follows:

Region: nt_dev

VOB storage: \\neptune\public\vega_project.vbs
VOB-tag: \vega
View storage: \\saturn\shared_views\int_43.vws
View-tag: int_43

Region: unix_dev

VOB storage: /net/neptune/public/vega_project.vbs
VOB-tag: /vobs/vega
View storage: /net/saturn/shared_views/int_43.vws
View-tag: int_43

Use the Regions subnode of the ClearCase Registry node in the ClearCase Administration Console to create, view, and remove regions. You can also use the mkregion, lsregion, and rmregion commands to create, view, and remove regions.

Registries in a Multiple-Region Network

Conceptually, each network region has its own view-tag registry and VOB-tag registry. Each VOB can have at most one tag in a region. In a network with two regions, each VOB or view has at most two tag entries.

Not every VOB or view needs a tag in every region. VOBs or views that are not used by all hosts only need tags in the region(s) used by the hosts that access them. By selectively excluding VOB-tags or view-tags from certain regions, you can use network regions to limit access to VOBs and views. (However, a VOB must have a tag in the region to which the VOB server host belongs, and a view must have a tag in the region to which the view storage directory's host belongs.)

It will simplify administration if you use the same text in the tag name in all regions. For example:

NOTE: In a mixed Windows and UNIX environment, VOB-tags that differ only in their initial directory separator character-backslash (\) or slash (/)- are equivalent.

This set of tags provides a standard way for users to refer to a VOB by name, even though the network file naming conventions are different.

Tag Registry Implementation

Figure 35 illustrates a simple two-region network, each with its own logical set of tag registries. All hosts in a network region use the same VOB-tags and view-tags, and access ClearCase data storage areas using the same pathnames, provided by registry lookups.

Figure 35 Network Regions and Their Tag Registries

Establishing Network Regions

The site preparation program (described in the Installation Guide for the ClearCase Product Family) prompts you to specify the name of a network region. This name becomes the default region, which can be accepted or overridden during ClearCase installation on individual hosts. To list a host's network region, use the host node of the ClearCase Administration Console, the ClearCase program in Control Panel, or the cleartool hostinfo -long command.