When an entry is removed in a Postgres database, the database marks the entry as invalid, but does not remove the entry from the database. There is a tool, /opt/novell/zenworks/bin/zlm-pq-vacuum, that can be run to purge the database of all removed items.
Run this tool periodically, or as a cron job to keep your database clean.
You should note that you may need to edit the zlm-pq-vacuum file to allow for silent execution of the tool. By following the instructions in the file you can have the tool bypass the prompt for the database password.