1)     Consider using if :   The history file becomes excessively large

2)      Consider using if:    Retention period is high

3)      Do not Delete “db2rhist.asc” or “db2rhist.bak”

4)     Do a proper analysis of restore requirements prior to PRUNE HISTORY

Example :  

Prior to the PUNE HISTORY

I execute the command :

PRUNE HISTORY 20110701 

This removed all entries for restores, loads, tables space backups and full database backups