Transactional data collected during the execution are periodically removed from the "live" transactional tables. It is common to retain order related information for extended periods of time. There are history tables provided for relevant transactional tables to move data from the day-to-day "live" tables to a historical table.
Purge is the process by which old data is removed from the system database. A purge minimizes the number of unused database records to increase search efficiency and reduces the size of the required physical disk.