Sometimes the CDC process of gathering data from the data sources cannot be precise enough to discern only the records that have been changed since it was last executed. Insert, modify, or delete data in the targets based on what data was gathered from the sources and what data exists in the targets. Gather the data that has been changed-inserted, modified, or deleted-in the data sources since the last time CDC process has been run. Unless all the data from the data sources is gathered and then indiscriminately loaded into the targets, for example, the targets are truncated to avoid duplicates and then all data is inserted, then CDC needs to: The CDC process needs to determine what data to access from data sources and updates its targets while typically retaining historical values.
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