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Cloned Objects
The cost of maintaining cloned objects is rarely discussed yet can contribute significant
storage costs. At the point of initial cloning, the original “parent” and cloned “child”
share the same micro-partitions. Assuming both parent and child are subject to different
DML actions using disparate data, the parent and child tables will diverge in content. But
what happens to the micro-partitions?
Micro-partitions for the parent will be superseded as expected with the full lineage
preserved according both Time Travel setting and Fail-Safe period.
Micro-partitions for the child untouched by DML activity for either parent or child
remain referenced back to the parent.
Figure 4-12 on the left shows both parent and child referencing the same micro-
partitions after cloning. On the right is the effect of DML activity to both the parent and
child showing how:
•
Micro-partitions are created where contents diverge.
•
Micro-partitions are moved to Time Travel where contents are
superseded.
Figure 4-12.
Cloned object storage consumption
Let’s investigate cloned object storage consumption using a practical example. You
will use
partsupp_baseline
and first check the allocated storage:
SELECT path_to_object,
active_GB,
time_travel_GB,
ChaPTer 4
MiCro-ParTiTionS