To find the system free space

/* Formatted on 2/12/2013 4:48:18 PM (QP5 v5.114.809.3010) */
SELECT F.TABLESPACE_NAME,
       TO_CHAR ((T.TOTAL_SPACE - F.FREE_SPACE),'999,999') "USED (MB)",
       TO_CHAR (F.FREE_SPACE, '999,999') "FREE (MB)",
       TO_CHAR (T.TOTAL_SPACE, '999,999') "TOTAL (MB)",
       TO_CHAR ((ROUND ((F.FREE_SPACE/T.TOTAL_SPACE)*100)),'999')||' %'
      PER_FREE
FROM   (
       SELECT       TABLESPACE_NAME,
                    ROUND (SUM (BLOCKS*(SELECT VALUE/1024
                                        FROM V$PARAMETER
                                        WHERE NAME = 'db_block_size')/1024)
                           ) FREE_SPACE
       FROM DBA_FREE_SPACE
       GROUP BY TABLESPACE_NAME
       ) F,
       (
       SELECT TABLESPACE_NAME,
       ROUND (SUM (BYTES/1048576)) TOTAL_SPACE
       FROM DBA_DATA_FILES
       GROUP BY TABLESPACE_NAME
       ) T
WHERE F.TABLESPACE_NAME = T.TABLESPACE_NAME
AND (ROUND ((F.FREE_SPACE/T.TOTAL_SPACE)*100)) < 10;

To find the status of object_type

SELECT  OWNER, OBJECT_NAME, OBJECT_TYPE, STATUS
FROM    DBA_OBJECTS
WHERE   STATUS = 'INVALID'
ORDER BY OWNER, OBJECT_TYPE, OBJECT_NAME;