https://github.com/jberet/jsr352/blob/master/jberet-core/src/main/java/org/jberet/repository/PurgeBatchlet.java removes only executions.
Instances are untouched.

When InMemoryRepository is used than it leads to OOM quite quickly.

In our scenario 6 jobs per second fill up 750MB in less than 24 hours and ends by OOM even we run PurgeBatchlet every minute (all completed jobs).