How to add comment dba_col_comments

SQL*Plus: Release 9.2.0.1.0 - Production on Sun Jan 25 21:59:52 2004

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SQL> conn /as sysdba;
Connected.
SQL>


SQL> desc dba_col_comments;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------

 OWNER                                     NOT NULL VARCHAR2(30)
 TABLE_NAME                                NOT NULL VARCHAR2(30)
 COLUMN_NAME                               NOT NULL VARCHAR2(30)
 COMMENTS                                           VARCHAR2(4000)

SQL> select comments from dba_col_comments where TABLE_NAME= 'DBA_FREE_SPACE';

COMMENTS
--------------------------------------------------------------------------------

Name of the tablespace containing the extent
ID number of the file containing the extent
Starting block number of the extent
Size of the extent in bytes
Size of the extent in ORACLE blocks
Relative number of the file containing the extent

6 rows selected.

SQL>
SQL> select comments from dba_col_comments where TABLE_NAME= 'TABLESPACE';

no rows selected


SQL> select comments from dba_col_comments where TABLE_NAME= 'DBA_SEGMENTS';

COMMENTS
-------------------------------------------------------------------------------

Username of the segment owner
Name, if any, of the segment
Partition/Subpartition Name, if any, of the segment
Type of segment:  "TABLE", "CLUSTER", "INDEX", "ROLLBACK",
"DEFERRED ROLLBACK", "TEMPORARY","SPACE HEADER", "TYPE2 UNDO"
 or "CACHE"

Name of the tablespace containing the segment
ID of the file containing the segment header
ID of the block containing the segment header
Size, in bytes, of the segment

COMMENTS
-------------------------------------------------------------------------------

Size, in Oracle blocks, of the segment
Number of extents allocated to the segment
Size, in bytes, of the initial extent of the segment
Size, in bytes, of the next extent to be allocated to the segment
Minimum number of extents allowed in the segment
Maximum number of extents allowed in the segment
Percent by which to increase the size of the next extent to be allocated
Number of process freelists allocated in this segment
Number of freelist groups allocated in this segment
Relative number of the file containing the segment header
The default buffer pool to be used for segments blocks

19 rows selected.

SQL>