What is the meaning of the IGNORE_DUP_KEY feature in SQL Server?

edit

The IGNOREDUPKEY feature in SQL Server is a constraint option that is used to indicate how duplicate rows should be treated when attempting to insert records into a table that has a unique constraint. If the IGNOREDUPKEY option is enabled, any duplicate records that are detected during an insert operation will be ignored and the remaining records will be inserted into the table. If the option is disabled, an error will be returned and the entire insert operation will be rolled back. This feature is often used to improve the performance of high-volume insert operations where duplicate records are expected, such as during data migration or data warehousing scenarios.