ABAP Keyword Documentation →  ABAP − Reference →  Processing Internal Data →  Internal Tables →  Internal Tables - Overview →  Table Keys → 

Duplicate Unique Keys

When rows are inserted into internal tables with a unique primary key or unique secondary key, duplicates can occur with respect to one or more of these keys. Depending on whether the insert takes place as a single record operation or a mass operation, the ABAP runtime environment responds as follows to an attempt to insert an entry with duplicate key values: