How to purge AUD$?

1. Count the number of rows
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select count(*) from AUD$;
it will show the number of rows

2. Then take the export backup
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NOTE:-export backup must be taken inside the perticular mountpoint where it's intended to keep the DMP file

exp file=/bkp/audit_bkp/exp_aud_Date.dmp log=/bkp/audit_bkp/exp_aud_Date.log tables=AUD$

password: / as sysdba

After Export Backup Check the number of rows the difference may b there.
There may or may n't b large difference

3.Clear the Table and Keep the Structure
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Truncate table AUD$

4.Check again
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select count(*) from AUD$;