Delete all data from schema

I use this

WITH const AS
  (SELECT rconst.table_name,
    rconst.constraint_name
     FROM user_constraints rconst,
    user_constraints pconst
    WHERE rconst.constraint_type = 'R'
  AND rconst.r_constraint_name   = pconst.constraint_name
  AND pconst.constraint_type     = 'P'  
  )
SELECT 'ALTER TABLE '||const.table_name||' DISABLE CONSTRAINT '||const.constraint_name||';' rnme FROM const UNION ALL
SELECT 'TRUNCATE TABLE '||ut.table_name||';' FROM user_tables ut UNION ALL 
SELECT 'ALTER TABLE ' ||const.table_name ||' ENABLE CONSTRAINT ' ||const.constraint_name ||';' rnme FROM const;

to generate script to clean schema.

• All rows from all tables will be removed.
• You can NOT rollback this script even if you replace "truncate" with "delete" (alter statement permorms commit). But you can use flashback to query truncated data.
• You can write a pl\sql block with loop, using this select as a cursor and execute immediate command.

You also can avoid ORA-02266 when you need to truncate table (replace 'T-A-B-L-E--N-A-M-E' with name of the table you need to truncate)

WITH const AS
  (SELECT rconst.table_name,
    rconst.constraint_name
     FROM user_constraints rconst,
    user_constraints pconst
    WHERE rconst.constraint_type = 'R'
  AND rconst.r_constraint_name   = pconst.constraint_name
  AND pconst.constraint_type     = 'P'
  AND pconst.table_name          = 'T-A-B-L-E--N-A-M-E'
  )
SELECT 'ALTER TABLE '||const.table_name||' DISABLE CONSTRAINT '||const.constraint_name||';' rnme FROM const UNION ALL
SELECT 'TRUNCATE TABLE '||const.table_name||';' FROM const UNION ALL 
SELECT 'ALTER TABLE ' ||const.table_name ||' ENABLE CONSTRAINT ' ||const.constraint_name ||';' rnme FROM const;