Simple Steps to Enable Extended Auditing in Oracle

Enabling auditing in db	sqlplus / as sysdba
	ALTER SYSTEM SET audit_trail=db,extended SCOPE=SPFILE;
	shutdown immediate
	startup
table for audit trails	DBA_AUDIT_TRAIL
view the size of audit	select round(bytes/1024/1024/1024) from dba_segments where segment_name ='AUD$';
see the current tablespace of audit table	select tablespace_name from dba_tables where table_name='AUD$';
Audit notes	Master Note For Oracle Database Auditing (Doc ID 1299033.1)
To audit a specific schema	AUDIT ALL STATEMENTS BY <username> ;
Moving $AUD table from SYSTEM TS to a dedicated Table Space	If your AUD$ table is in SYSTEM and SYSTEM tablespace, Then it is advised to move the AUD$to a dedicated tablespace.
Use steps to move AUD$.	select owner,segment_name,segment_type,tablespace_name,bytes/1024/1024 from dba_segments where segment_name='AUD$';
	OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME BYTES/1024/1024
	------- ------------- ------------ ---------------- ----------------
	SYS AUD$ TABLE SYSTEM 16
Use the dbms_audit_mgmt to move the tablespace.	BEGIN
	DBMS_AUDIT_MGMT.SET_AUDIT_TRAIL_LOCATION(audit_trail_type => DBMS_AUDIT_MGMT.AUDIT_TRAIL_AUD_STD,
	audit_trail_location_value => 'AUDIT_DATA');
	END;
	/
	PL/SQL procedure successfully completed.
check whether tablespace has been moved from system to AUDIT_DATA or not.	select owner,segment_name,segment_type,tablespace_name,bytes/1024/1024 from dba_segments where segment_name='AUD$';
	OWNER SEGMENT_NAME SEGMENT_TYPE TABLESPACE_NAME BYTES/1024/1024
	------- ------------- ------------------ ------------------------------ ---------------
	SYS AUD$ TABLE AUDIT_DATA 16
REFERENCE:	http://oracle-help.com/oracle-12c/oracle-12cr2/move-aud-table-another-tablespace-using-dbms_audit_mgmt/?lipi=urn%3Ali%3Apage%3Ad_flagship3_feed%3BE90F%2Fb6fSWuTqaWMugxZQw%3D%3D