Indexes on Oracle8i Release 8.1.7.0.0 - Production

Quick query,
I have noticed that the size of the column field on ALL_IND_COLUMNS and USER_IND_COLUMNS is 4000 charatcers in length, but a column can only be 30 characters.
Does anyone know hwy there is such a bit difference in these 2 columns, surely the 4000 only neds to be 30.
This is apperent on all 8 version databases we have installed.

The reason I looked into this is I am tring to look at a performance issue with 1 of our databases and don't know if this is contributing to the problem.

Regards

    Anthony Millard

SQL> DESC ALL_IND_COLUMNS

 Name                            Null?    Type


 ------------------------------- -------- ----

 INDEX_OWNER                     NOT NULL VARCHAR2(30)
 INDEX_NAME                      NOT NULL VARCHAR2(30)
 TABLE_OWNER                     NOT NULL VARCHAR2(30)
 TABLE_NAME                      NOT NULL VARCHAR2(30)
 COLUMN_NAME                              VARCHAR2(4000)
 COLUMN_POSITION                 NOT NULL NUMBER
 COLUMN_LENGTH                   NOT NULL NUMBER
 DESCEND                                  VARCHAR2(4)

SQL> desc all_tab_columns
 Name                            Null?    Type


 ------------------------------- -------- ----

 OWNER                           NOT NULL VARCHAR2(30)
 TABLE_NAME                      NOT NULL VARCHAR2(30)
 COLUMN_NAME                     NOT NULL VARCHAR2(30)
 DATA_TYPE                                VARCHAR2(106)
 DATA_TYPE_MOD                            VARCHAR2(3)
 DATA_TYPE_OWNER                          VARCHAR2(30)
 DATA_LENGTH                     NOT NULL NUMBER
 DATA_PRECISION                           NUMBER
 DATA_SCALE                               NUMBER
 NULLABLE                                 VARCHAR2(1)
 COLUMN_ID                       NOT NULL NUMBER
 DEFAULT_LENGTH                           NUMBER
 DATA_DEFAULT                             LONG
 NUM_DISTINCT                             NUMBER
 LOW_VALUE                                RAW(32)
 HIGH_VALUE                               RAW(32)
 DENSITY                                  NUMBER
 NUM_NULLS                                NUMBER
 NUM_BUCKETS                              NUMBER
 LAST_ANALYZED                            DATE
 SAMPLE_SIZE                              NUMBER
 CHARACTER_SET_NAME                       VARCHAR2(44)
 CHAR_COL_DECL_LENGTH                     NUMBER
 GLOBAL_STATS                             VARCHAR2(3)
 USER_STATS                               VARCHAR2(3)
 AVG_COL_LEN                              NUMBER

Version Details
Oracle8i Release 8.1.7.0.0 - Production
PL/SQL Release 8.1.7.0.0 - Production
CORE 8.1.7.0.0 Production
TNS for 32-bit Windows: Version 8.1.7.0.0 - Production NLSRTL Version 3.4.1.0.0 - Production Received on Mon Oct 08 2001 - 05:42:29 CDT