MMON automatically deletes AWR snaps if SYSAUX is full

Interesting find in an alert log indicating that MMON tries to purge old data when SYSAUX is full :-

Thu Apr 29 16:00:03 2010
ORA-1688: unable to extend table SYS.WRH$_ACTIVE_SESSION_HISTORY partition WRH$_ACTIVE_2503051407_14753 by 128 in tablespace SYSAUX
MMON Flush encountered SYSAUX out of space error(1688).
MMON (emergency) purge of WR snapshots (14690) and older
Thu Apr 29 16:00:49 2010
ORA-1688: unable to extend table SYS.WRH$_ACTIVE_SESSION_HISTORY partition WRH$_ACTIVE_2503051407_14753 by 128 in tablespace SYSAUX
MMON Flush encountered SYSAUX out of space error(1688).
MMON (emergency) purge of WR snapshots (14705) and older