Consider a fast load job that maintains checkpoint of 10,000.The fast load stops at 15,000th record.Now the fast load when restarted will restart from the checkpoint ie.10,001th record.Now from 10,001th record upto 15,000 records data will be already loaded into target table but when restarted the records will go into target table from 15,001th record onwards.How is possible to load data into target table when the data is already loaded.because fast load loads into empty table.
The fastload only loads data into empty tables. when a job fails after a certain checkpoint and when the job is rerun, this does not mean that the table has data in it. The table is still in loading phase and it cannot be accessed. hope this helps.