The Sequence Generator transformation is a passive transformation that generates numeric values. Use the Sequence Generator transformation to create unique primary key values, replace missing primary keys, or cycle through a sequential range of numbers.

The Sequence Generator transformation is a connected transformation. It contains two output ports that you can connect to one or more transformations. The Integration Service generates a block of sequence numbers each time a block of rows enters a connected transformation. If you connect CURRVAL, the Integration Service processes one row in each block. When NEXTVAL is connected to the input port of another transformation, the Integration Service generates a sequence of numbers. When CURRVAL is connected to the input port of another transformation, the Integration Service generates the NEXTVAL value plus the Increment By value.

You can create a Sequence Generator transformation to use in a single mapping, or you can create a reusable Sequence Generator transformation to use in multiple mappings. A reusable Sequence Generator transformation maintains the integrity of the sequence in each mapping that uses an instance of the Sequence Generator transformation.

You can make a Sequence Generator transformation reusable, and use it in multiple mappings. You might reuse a Sequence Generator transformation when you perform multiple loads to a single target.

For example, if you have a large input file that you separate into three sessions running in parallel, use a Sequence Generator transformation to generate primary key values. If you use different Sequence Generator transformations, the Integration Service might generate duplicate key values. Instead, use the reusable Sequence Generator transformation for all three sessions to provide a unique value for each target row.