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Course 3067 - Novell eDirectory 8.8 Design & Implementation:
Subordinate Reference
Subordinate reference (SR) replicas are system-generated replicas that don't contain all the object data of a master or a R/W replica.
SR replicas, therefore, don't provide fault tolerance.
They are internal pointers that are generated to contain enough information for eDirectory to resolve object names across partition boundaries.
You can't delete an SR replica; eDirectory deletes it automatically when it is not needed. SR replicas are created only on servers that hold a replica of a parent partition but no replicas of its child partitions.
If a replica of the child partition is copied to a server holding the replica of the parent, the SR replica is automatically deleted.
They contain only the partition root object. They only exist to provide a link between the parent partition and its child partition.
eDirectory creates an SR replica on a server when the server holds a
real parent partition and but does not hold a
real child partition of that parent partition.
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Real refers to a Master, Read/Write, Read-Only, or filtered replica. An SR replica is not a real replica.
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When you define the partitions and replicas for your tree, consider a strategy that minimizes SR replicas showing up in your tree. This is, however, more of guideline than a hard and fast rule because SR replicas are handled better in current versions of eDirectory.
As a rule of thumb, when a parent partition is placed as a replica on a server, a replica of the child partition exists automatically as a SR unless you have identified it as another type of replica, as shown in the following:
To minimize SRs, you need to understand why they automatically appear in certain locations:
■ When a parent partition is placed as a replica on a server, eDirectory automatically places SRs on that server connecting the parent partition to its child partitions. An SR is not placed to connect to its grandchild partitions. Figure 4-4 shows 3 partitions under a parent partition.
■ An SR replica will not show up if a replica of the (R/W or R-O) child partition exists on the same server as the replica of the parent partition.
■ Replicas of child partitions do not require a replica of the parent partition.
Because SRs are copies of partition root objects, they hold the replica attribute, which is a list of servers that are in the replica list. eDirectory uses this list to locate replicas of other servers who hold replicas of the partition for tree walking purposes.