[oracle@sjzx00 ~]$ cat clear_arch.sh 
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/10.2.0
export ORACLE_TERM=xterm
export NLS_LANG=AMERICAN_AMERICA.UTF8
export ORACLE_SID=orcl
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME/lib:/lib:/usr/lib:/usr/local/lib
rman target / nocatalog log=/home/oracle/delete_archive.log <<EOF
allocate channel for maintenance type disk;
crosscheck archivelog all;
delete  noprompt expired archivelog all;
delete noprompt archivelog until  time 'sysdate-2';
exit;
EOF

前面这些环境变量可以不需要设置，但是前提是这台主机上只有一个数据库实例，有多个实例就要设置环境变量了。

corntab脚本 
root用户：crontab -e
* * * * * su - oracle -c  /home/oracle/clear_arch.sh >>/home/oracle/delete_arch.log &