When you have a reusable Sequence Generator transformation in several sessions and the sessions run at the same time, use Number of Cached Values to ensure each session receives unique values in the sequence. By default, Number of Cached Values is set to 1000 for reusable Sequence Generators.
When multiple sessions use the same Sequence Generator transformation at the same time, you risk generating the same values for each session. To avoid this, have the Integration Service cache a set number of values for each session by configuring Number of Cached Values.
For example, you configure a reusable Sequence Generator transformation as follows: Number of Cached Values = 50, Current Value = 1, Increment By = 1. Two sessions use the Sequence Generator, and they are scheduled to run at approximately the same time. When the Integration Service starts the first session, it caches 50 values for the session and updates the current value to 50 in the repository. The Integration Service begins using values 1 to 50 in the session. When the Integration Service starts the second session, it checks the repository for the current value, which is 50. It then caches the next 50 values and updates the current value to 100. It then uses values 51 to 100 in the second session. When either session uses all its cached values, the Integration Service caches a new set of values and updates the current value to ensure these values remain unique to the Sequence Generator.
For reusable Sequence Generator transformations, you can reduce Number of Cached Values to minimize discarded values, however it must be greater than one. When you reduce the Number of Cached Values, you might increase the number of times the Integration Service accesses the repository to cache values during the session.