Some processing rules for the Spark engine differ from the processing rules for the Data Integration Service.
Mapping validation fails in the following situations:
The transformation contains stateful variable ports.
The transformation contains unsupported functions in an expression.
If you use a port in an expression in the Aggregator transformation but you do not use the port within an aggregate function, the run-time engine might use any row in the port to process the expression.
The row that the run-time engine uses might not be the last row in the port. Processing is distributed, and thus the run-time engine might not be able to determine the last row in the port.
Data Cache Optimization
You cannot optimize the data cache for the transformation to store data using variable length.