How to handle org.apache.sqoop.validation.RowCountValidator in live RDBMS system?

[#1]

I thought org.apache.sqoop.validation.RowCountValidator will take count while sqoop retrieve records from source, but its taking count after the MR completes. How to handle this in live RDBMS?How to handle this?

Also, How to use Percentage Tolerant? Reference: https://sqoop.apache.org/docs/1.4.6/SqoopUserGuide.html

[#2]

Did you used --validate parameter in sqoop?.If not it may be useful for your scenario.