delete old audit sys records

Dear All,

We use a audit_trail OS.

SQL> show parameter audit;

NAME

TYPE

VALUE

-------------------- ------- --------------------------------------------

audit_file_dest	string  /data/app/11.2.0.4/adminora/admin/cmsp/adump
audit_sys_operations	boolean TRUE
audit_syslog_level	string
audit_trail	string  OS

Show parameters query failed

Problem: OS log file keeps growing in size too fast...

Could you tell me how to keep records just for 5 days and delete all records beyond to 5 day??

Thank you all in advance.