DIRECTORY SERVICES
Servers can use the directory assistance failover method, rather than cluster failover method, to find an available replica of a Domino Directory or Extended Directory Catalog. To use the directory assistance failover method, on the Replicas tab of the Directory Assistance document for the directory, specify up to five replicas of the directory that are potentially available for use.
When a server starts up, directory assistance searches for an available replica among the replicas you have specified. If directory assistance cannot find an available replica during server startup, in five minutes it attempts to locate an available replica again, continuing this attempt at five-minute intervals until successful.
Once directory assistance finds an available replica at server startup, it continues to use the replica unless the replica becomes unavailable, at which point failover occurs and directory assistance looks for an alternate replica. When a replica is unavailable for any reason, directory assistance continues to use the alternate replica, even after the previously unavailable replica becomes available.
Directory assistance finds that a replica is unavailable if it attempts to access the replica during server startup, or during normal server operation when it processes a client lookup request. A directory replica is unavailable to directory assistance if:
At server startup and during failover, directory assistance looks for an available replica from the list of replicas specified in the Directory Assistance document as follows:
1. Looks for a local replica.
2. Looks for a replica within the same Notes named network; if there is more than one, looks in the order in which the Directory Assistance document lists them.
3. Looks for a replica within the same Domino Domain; if there is more than one, looks in the order in which the Directory Assistance document lists them.
4. Looks for a replica it hasn't looked for yet.
The cluster failover method for directory assistance
If replicas of a Domino Directory or Extended Directory Catalog configured in the directory assistance database are on servers that are members of a cluster, you can set up directory assistance to use cluster failover and workload balancing instead of the directory assistance failover method. To use cluster failover and workload balancing, in the Replicas tab of the Directory Assistance document for the directory specify only one of the directory replicas that is within the cluster. Be sure to specify only one replica; if you specify more than one, directory assistance ignores cluster failover, and instead uses the directory assistance failover method described above to find an available replica.
Cluster failover is particularly useful in environments with centralized directory services. For example, you can configure cluster failover in a Directory Assistance document for a remote primary Domino Directory, so that servers with Configuration Directories use cluster failover to find an available replica of the remote primary directory.
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