Sequence Generator transformation is used to generate a sequence of unique numbers. Based on the property defined in the Sequence Generator transformation, the unique values are generated. A sample mapping showing the Sequence Generator transformation in shown in the following screnshot:
As you can notice in the mapping, the Sequence Generator transformation does not have any input port. You need to define the Start value, Increment by value, and End value in the properties. Based on properties, the sequence generator generates the value. In the preceding mapping, as soon as the first record enters the target from the Source Qualifier transformation, NEXTVAL generates its first value and so on for other records. The sequence Generator is built for generating numbers.