Some projects fail at the last minute because software was tested with invented data.
A company which was running the JCC LogMiner Loader for the production Rdb databases wanted to test a possible replacement for downstream databases and applications. The Loader was used to run transactions packaged from the AIJs. These were then run in real time emulation.
The Loader does not emulate the read only work, but can emulate all of the write activity. The write activity can then be run, as if it were a live feed, in emulation of real time. If the software being tested passes the real time test, the Loader can then be set to deliver the writes twice as fast as they were written in production to test scalability. Other settings for faster and slower are also possible.
In fact, JCC developed this mode of operation because the people working on the new project requested a way to slow down the feed. Regrettably, the software being tested was never tuned to the performance required for the envisioned tasks. The testing avoided costly error through the introduction of something that couldn't keep up.