VOB families with unidirectional synchronization

This topic describes how to raise the feature level for a VOB family, where unidirectional synchronization is in effect.

In some VOB families, one or more replicas may be one-way replicas. These replicas import packets, but they do not export packets to any other replicas in the family, and therefore cannot communicate changes in feature level. Because other replicas in the family do not know the current feature level of the one-way replicas, the chflevel –family command fails.

For example, consider the case of two replicas, R1 and R2, that constitute a VOB family. R1 sends update packets to R2, but R2 does not send update packets to R1.

R1 is at replica feature level 4, and R2 is at replica feature level 3. Therefore, the family feature level is 3 and cannot be raised. Now suppose R2’s replica feature level is raised to 4. R2 cannot communicate the change in feature level to R1 because it does not export update packets.

Because both replicas are now at feature level 4, the VOB family feature level can be raised to 4. However, if the R1 administrator issues the command chflevel -family 4 vob-selector, the change fails because R1 does not know that the replica feature level at R2 has been raised.

In this case, the R2 administrator must inform the R1 administrator of the change in R2’s replica feature level. The R1 administrator then uses a special form of the chflevel command to raise the VOB family feature level. The general procedure is as follows:
  1. The administrator of a one-way replica notifies other replica administrators in the VOB family of a change in replica feature level at the one-way replica.
  2. At the replica that masters the VOB object, the administrator enters the following command: 
    cleartool chflevel –force –override –family feature-level vob:vob-tag
    Attention: This form of the chflevel command bypasses the constraint that the family feature level is no higher than the lowest known feature level of the replicas in the VOB family. Use it only when you are certain that all replicas in the VOB family are at the same feature level. If you use this command inappropriately, synchronization will fail.
  3. At the replica that masters the VOB object, export update packets to all replicas in the family.