CHECKPOINT ISOLATED LOADING Usage Notes

The CHECKPOINT ISOLATED LOADING statement must be issued by the same session as the BEGIN ISOLATED LOADING statement.
When you issue the CHECKPOINT ISOLATED LOADING statement, the data that has been loaded up to that point by the session, or by all sessions in a multi-session load operation, is committed and becomes available for concurrent read operations. You can use the CHECKPOINT ISOLATED LOADING statement to enable recently loaded data to be available for concurrent read operations while the load operation continues.
The CHECKPOINT ISOLATED LOADING statement must be the last statement in an explicit transaction.

CHECKPOINT ISOLATED LOADING Usage Notes - Teradata Database