VOBs and VOB replicas

In DevOps Code ClearCase® MultiSite, a VOB replica is a copy of a VOB, including both file system data (data containers) and metadata (VOB database). At each replica, developers can see all VOB elements and all versions of each element.

Each replica has a replica name in addition to a VOB tag. You specify both the replica name and the VOB tag when you create the replica. For each replica, the VOB database contains a replica object that records the name of the replica. The VOB database also tracks the location of each replica by host name. This tracking enables DevOps Code ClearCase MultiSite administrators to specify replicas at other sites with short, mnemonic identifiers without needing to know their exact locations.

The replicas are not necessarily exact copies of each other. DevOps Code ClearCase MultiSite features accommodate typical differences among sites:
  • Different hosts at a site may have different user spaces defined by the local password and group databases. You can configure particular replicas to ignore identities and permissions differences or to propagate changes to identities and permissions. For more information, see Identities and permissions strategy for VOB replicas.
  • Disk configurations and capacities may vary. Accordingly, you can manage VOB storage pools independently at each replica host.
  • Different sites may have different development policies and can use site-specific scripts to enforce them. For this reason, DevOps Code ClearCase triggers are not propagated.

Most, but not all, of the information stored in a VOB is replicated. All changes that create new data, remove old data, and move or rename existing data are propagated among the replicas in the VOB family. However, information stored in views is not propagated. For example, a replica update includes the fact that an element has been checked out, because the checkout is recorded in the VOB; but the update does not include the contents of the checked-out version.

For more information, see Information propagated among VOB replicas.

Allowing differences among replicas reflects the basic capability of DevOps Code ClearCase MultiSite: enabling development work to proceed independently at different locations. For more information, see Independent development: Mastership.