Keeping indexes on a table causes the bulk copy utility to use slow bcp automatically. However, slow bcp can fill the transaction log very quickly.
When you are copying a large number of rows, the performance penalty and log space requirements for using slow bcp can be severe.
For extremely large tables, using slow bcp is not an option because its detailed log makes it much too slow.
To improve the performance of bcp:
Use partitioned tables. Several bcp sessions with a partitioned table can reduce dramatically the time required to copy the data. However, such performance improvements are more noticeable in fast bcp than in slow bcp.
Use bcp in parallel to increase performance dramatically. Parallel bulk copy can provide balanced data distribution across partitions. For more information, see “Using parallel bulk copy to copy data into a specific partition”.
