Somehow this question slipped my last years Odd things (on OTN) series, so I decided to collect several methods for this problem. Sort of a reverse String Aggregation Techniques. ;-)

Version 1: CONNECT BY (taken from MODEL clause vs. old school SQL)

WITH t AS (SELECT '10,12,20,30,30,3,12,12,56' col1
             FROM dual
          )
SELECT SUBSTR(col1
             ,DECODE(level, 1, 1, INSTR(col1,',',1,level-1)+1)
             ,DECODE(INSTR(col1,',',1,level), 0, LENGTH(col1), instr(col1,',',1,level)
             -DECODE(level, 1, 0, INSTR(col1,',',1,level-1))-1)
             ) col_new
  FROM t
  CONNECT BY level < LENGTH(REPLACE(TRANSLATE(col1,'01234567890','00000000000'),'0')) + 2
; 
COL_NEW
----------
10
12
20
30
30
3
12
12
56

WITH t AS (SELECT '10,12,20,30,30,3,12,12,56' col1
             FROM dual
          )
SELECT REGEXP_SUBSTR(col1, '[^,]+', 1, ROWNUM) col_new
  FROM t
  CONNECT BY level <= LENGTH(REGEXP_REPLACE(col1, '([^,])+|.', '\1'))
; 

COL_NEW
----------
10
12
20
30
30
3
12
12
56

CREATE OR REPLACE PACKAGE utl_strings
AS
  TYPE t_outtab IS TABLE OF VARCHAR2(255);
  
  FUNCTION str_to_rows(
    p_string IN VARCHAR2             -- source string
  , p_delim  IN VARCHAR2 DEFAULT ',' -- delimiteter 
  ) RETURN t_outtab PIPELINED
  ;
END utl_strings;
/ 
 
CREATE OR REPLACE PACKAGE BODY utl_strings
AS
  FUNCTION str_to_rows(
    p_string IN VARCHAR2             -- source string
  , p_delim  IN VARCHAR2 DEFAULT ',' -- delimiteter 
  ) RETURN t_outtab PIPELINED
  IS
    v_start   NUMBER := 1;
    v_len     NUMBER := NVL(LENGTH(p_string), 0);
    v_pos     NUMBER;
  BEGIN  
    WHILE v_start <= v_len 
    LOOP
      v_pos := INSTR(p_string, p_delim, v_start);  
    
      IF v_pos = 0 THEN 
         v_pos := v_len + 1;
      END IF;
         
      PIPE ROW(SUBSTR(p_string, v_start, v_pos - v_start));
      
      v_start := v_pos + 1;   
    END LOOP;  
  END str_to_rows;  
END utl_strings;
/ 

SELECT column_value col_new
  FROM TABLE(utl_strings.str_to_rows('10,12,20,30,30,3,12,12,56'))
;

COL_NEW
----------
10
12
20
30
30
3
12
12
56

WITH t AS (SELECT '10,12,20,30,30,3,12,12,56' col1
             FROM dual
          )
SELECT col_new
  FROM t
 MODEL
   PARTITION BY (ROWNUM rn)
   DIMENSION BY (0 dim)
   MEASURES(col1, col1 col_new)
   RULES ITERATE(99) UNTIL (ITERATION_NUMBER = LENGTH(REGEXP_REPLACE(col1[0], '[^,]')))
                (col_new[ITERATION_NUMBER] = REPLACE(REGEXP_SUBSTR(col1[0], '(^|,)[^,]*', 1, ITERATION_NUMBER+1), ','))
;

COL_NEW
----------
10
12
20
30
30
3
12
12
56

After checking the current size of my XE instance in my yesterday's blog I decided to take a closer look at SYSTEM and SYSAUX tablespace:

SELECT tablespace_name
     , SUM(bytes / 1024 / 1024) size_mb
  FROM dba_segments
 WHERE tablespace_name IN ('SYSAUX', 'SYSTEM')
 GROUP BY tablespace_name
;

TABLESPACE_NAME                   SIZE_MB
------------------------------ ----------
SYSAUX                           764,4375
SYSTEM                           434,6875

SELECT segment_name 
     , segment_type
     , bytes / 1024 / 1024 size_mb
  FROM dba_segments
 WHERE tablespace_name = 'SYSTEM'
 ORDER BY bytes DESC
;

SEGMENT_NAME                   SEGMENT_TYPE          SIZE_MB
------------------------------ ------------------ ----------
SOURCE$                        TABLE                     143
IDL_UB1$                       TABLE                      42
IDL_UB2$                       TABLE                      15
C_OBJ#_INTCOL#                 CLUSTER                    11
C_TOID_VERSION#                CLUSTER                    10
PK_C0                          INDEX                      10
PK_O                           INDEX                      10
PK_CT                          INDEX                      10
PK_CS                          INDEX                      10
ARGUMENT$                      TABLE                       7

SELECT segment_name 
     , segment_type
     , bytes / 1024 / 1024 size_mb
  FROM dba_segments
 WHERE tablespace_name = 'SYSAUX'
 ORDER BY bytes DESC
;

SEGMENT_NAME                   SEGMENT_TYPE          SIZE_MB
------------------------------ ------------------ ----------
SYS_LOB0000010794C00025$$      LOBSEGMENT                 58
WWV_FLOW_PAGE_PLUGS            TABLE                      30
WWV_FLOW_STEP_ITEMS            TABLE                      27
I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST INDEX                      22
WRI$_OPTSTAT_HISTGRM_HISTORY   TABLE                      14
WWV_FLOW_REGION_REPORT_COLUMN  TABLE                      12
SYS_LOB0000012406C00009$$      LOBSEGMENT                 12
WWV_FLOW_STEP_PROCESSING       TABLE                      11
WWV_FLOW_PAGE_PLUGS            TABLE                      11
SYS_LOB0000012186C00017$$      LOBSEGMENT                 11