If AUDIT_TRAIL is not set to NONE then using the following SQL one can find the statements that have auditing turned on.
SQL> SELECT * FROM dba_stmt_audit_opts union SELECT * FROM dba_priv_audit_opts;
AUDIT_OPTION SUCCESS FAILURE
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ALTER ANY PROCEDURE BY ACCESS BY ACCESS
ALTER ANY TABLE BY ACCESS BY ACCESS
ALTER DATABASE BY ACCESS BY ACCESS
This is not enough. Please give detail about any topic like what is audit, how types of auditing is possible, how to audit a database etc.