Teradata Multiload

Multiload is a Teradata utility that will read a unix file and update (insert, delete, update) a populated target table.

Multiload is faster than Bteq for updating a populated table. Bteq updates 1 row at a time, where Multiload updates blocks of rows at a time.

When Multiload is compared to the Fastload/delete/insert method, then Multiload is faster for volumes above 10,000 records. For volumes less than 10,000 records, the difference is seconds, and is negligible. Multiload is faster whether the target table has a unique primary index, or a non-unique primary index. 

The Fastload/delete/insert method of updating populated target tables consists of 3 steps:

 1) Fastload into a temporary table

 2) Bteq delete matching rows from the target table

 3) Bteq insert into the target table. 

Multiload skips the temporary table and directly updates the target table from the unix file.

When loading into an empty target table, both Multiload and Fastload are about the same speed.

Multiload’s speed is not affected by the number of rows already in the target table. The speed is affected by the number of  update records, and can be affected by the number of error records written to the error journals. 

Upsert performs the same functionality as the delete/insert.

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