4.2 Under the Hood: What Happens When You Update a View

When you start an update operation, ClearCase compares the version of the elements loaded in the view with the version the config spec selects in the VOB. If the config spec selects a version in the VOB that is different from the version loaded in your view, ClearCase copies the version from the VOB into your view (Figure 18). ClearCase does not make this comparison or otherwise modify versions currently checked out to the view.

The update operation takes into account the fact that changes may be occurring in the VOB during the update. As ClearCase updates your view, other developers may check in new versions of elements your view's load rules select. To avoid loading an inconsistent set of versions, the update operation ignores versions in the VOB that meet both of the following conditions:

• The version was checked in after the moment the update began.

• The version is now selected by a config spec rule that involves the LATEST version label.

The update operation adjusts for the possibility that the system clocks on different hosts in a network may be out of sync (clock skew).

Figure 18 The Update Operation