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Title
In SharePlex replication involving one-way replication what constraints need to be enabled on target database? -
Description
In SharePlex replication involving one-way replication what constraints need to be enabled on target database?
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Cause
General information. -
Resolution
In a one-way replication, the constraints on the target can be dealt with as follows:
The Primary key or a unique key is desired on target for the purpose of efficiency of posting.
The referential integrity constraints can remain disabled on target as they are enforced on source anyway. This will improve the efficiency of posting.
The ON DELETE CASCADE constraint should not be enabled on target as they would report out of sync errors even though such errors are a false alarm and in SharePlex terminology they are designated as “false” out of sync. The reason for this is, the constraint is already enforced on source and the child record is already deleted on source. This deletion of child record is replicated across and the target child row is also deleted. If the constraint is also enabled on target, SharePlex will attempt to delete the child record once again and would fail to do so as the record has already been deleted by virtue of replication. This is termed as “false” out of sync. Same apply to Oracle trigger.
The CHECK constraints are undesirable as they slow down posting. Since they are enforced on source anyway, one can do away with them on target.