Schema mapping is done when the physical schema in the target system is not the same as the physical schema in the source system.
As mentioned earlier, suppose we are moving components from Development System (DEV) to Production System (PROD).
The tables in DEV reside in DEV_SCHEMA and the same tables reside in PROD system in PROD_SCHEMA schema. If an attribute view is transported from DEV to PROD, it will not work because the schema name is referenced in the definition of attribute view. In order for the promoted objects to work in PROD, schema mapping needs to be set up in the target system.

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