ORACLE AUDIT

Dear All,
Currently im running a 9.2.0.8.0 version. my audit parameters show as follows

SQL> show parameter audit;

NAME                                 TYPE        VALUE
------------------------------------ ----------- -------------------
audit_file_dest                      string      ?/rdbms/audit
audit_sys_operations                 boolean     FALSE
audit_trail                          string      TRUE
transaction_auditing                 boolean     TRUE

Q1. i need to enable audit_sys_operations.
Q2. what is the impact if i disable transaction_auditing.
Q3. difference between  audit_trail and transaction_auditing

Thanks
Kaushal Fernando