5.1 Overview of Feature Levels

Feature levels allow different replica hosts in a VOB family to run different versions of Rational ClearCase. New versions of ClearCase may introduce features that are incompatible with old versions, but administrators may not be able to upgrade all replica hosts at the same time. Feature level control enables you to upgrade replica hosts at different times and to prevent developers from using new ClearCase features that are not meaningful to replicas on hosts running earlier versions.

Each version of ClearCase has a feature level. Each VOB family has a single feature level called the family feature level. Each replica in the family has a feature level called the replica feature level. Thus, each VOB family has one family feature level and possibly several replica feature levels. The family feature level determines which ClearCase features can be used by all of the replicas in the family. The following constraints are enforced:

• The replica feature level is less than or equal to the feature level of the version of ClearCase installed on the replica's server host.

Different replicas on the same server host can have different feature levels.

• The family feature level is less than or equal to the lowest replica feature level found among replicas in the VOB family. Figure 18 shows an example.

Figure 18 VOB Family Feature Levels

The general procedure for raising a family's feature level is as follows:

1. Install the new version of ClearCase on the server hosts of replicas in the VOB family.

2. Raise the feature level of each replica in the VOB family. See Raising the Replica Feature Level.

3. Raise the feature level of the VOB family. See Raising the VOB Family Feature Level.

You can complete these steps incrementally and over a period of days or weeks, if necessary. Variations are possible; for example, if a VOB family has replicas R1 and R2 on servers S1 and S2, respectively, you can install a new version of ClearCase on S1 and raise R1's replica feature level before installing the new version on S2. However, you can complete Step #3 only after you have raised all replicas in the family to the new feature level.

For information about the feature level associated with the current version of ClearCase, and the list of features that are disabled until the VOB family feature level is raised, see the Release Notes for Rational ClearCase and ClearCase MultiSite.