Don't be impatient: we're getting closer.
Our next digression on the way to metadata is on the issue of scrubbers. You noticed the plural? Yes, there are two, typically scheduled as tasks:
We shall be concerned here with the latter, so let's talk of the former first.
The scrubber (already mentioned in the Removing derived objects section of Chapter 3, Build Auditing, and Avoidance) takes care of maintaining the pools within reasonable disk space limits. Actually only two of the three pools: the cleartext and the do pools. Pools are directory trees in the vob storage outside the database that contain the actual data. The third is the source pool which stores versions of file elements. We'll review the most interesting ...