Its all there in the dictionary
SQL> create table t ( x int, y date, z varchar2(10));
Table created.
SQL>
SQL> alter table t set unused column y;
Table altered.
SQL> alter table t set unused column z;
Table altered.
SQL>
SQL> select *
2 from user_tab_cols
3 where table_name = 'T'
4 @pr
==============================
TABLE_NAME : T
COLUMN_NAME : X
DATA_TYPE : NUMBER
DATA_TYPE_MOD :
DATA_TYPE_OWNER :
DATA_LENGTH : 22
DATA_PRECISION :
DATA_SCALE : 0
NULLABLE : Y
COLUMN_ID : 1
DEFAULT_LENGTH :
DATA_DEFAULT :
NUM_DISTINCT :
LOW_VALUE :
HIGH_VALUE :
DENSITY :
NUM_NULLS :
NUM_BUCKETS :
LAST_ANALYZED :
SAMPLE_SIZE :
CHARACTER_SET_NAME :
CHAR_COL_DECL_LENGTH :
GLOBAL_STATS : NO
USER_STATS : NO
AVG_COL_LEN :
CHAR_LENGTH : 0
CHAR_USED :
V80_FMT_IMAGE : NO
DATA_UPGRADED : YES
HIDDEN_COLUMN : NO
VIRTUAL_COLUMN : NO
SEGMENT_COLUMN_ID : 1
INTERNAL_COLUMN_ID : 1
HISTOGRAM : NONE
QUALIFIED_COL_NAME : X
USER_GENERATED : YES
DEFAULT_ON_NULL : NO
IDENTITY_COLUMN : NO
EVALUATION_EDITION :
UNUSABLE_BEFORE :
UNUSABLE_BEGINNING :
COLLATION :
COLLATED_COLUMN_ID :
==============================
TABLE_NAME : T
COLUMN_NAME : SYS_C00002_18101512:00:28$
DATA_TYPE : DATE
DATA_TYPE_MOD :
DATA_TYPE_OWNER :
DATA_LENGTH : 7
DATA_PRECISION :
DATA_SCALE :
NULLABLE : Y
COLUMN_ID :
DEFAULT_LENGTH :
DATA_DEFAULT :
NUM_DISTINCT :
LOW_VALUE :
HIGH_VALUE :
DENSITY :
NUM_NULLS :
NUM_BUCKETS :
LAST_ANALYZED :
SAMPLE_SIZE :
CHARACTER_SET_NAME :
CHAR_COL_DECL_LENGTH :
GLOBAL_STATS : NO
USER_STATS : NO
AVG_COL_LEN :
CHAR_LENGTH : 0
CHAR_USED :
V80_FMT_IMAGE : NO
DATA_UPGRADED : YES
HIDDEN_COLUMN : YES
VIRTUAL_COLUMN : NO
SEGMENT_COLUMN_ID : 2
INTERNAL_COLUMN_ID : 2
HISTOGRAM : NONE
QUALIFIED_COL_NAME : SYS_C00002_18101512:00:28$
USER_GENERATED : NO
DEFAULT_ON_NULL : NO
IDENTITY_COLUMN : NO
EVALUATION_EDITION :
UNUSABLE_BEFORE :
UNUSABLE_BEGINNING :
COLLATION :
COLLATED_COLUMN_ID :
==============================
TABLE_NAME : T
COLUMN_NAME : SYS_C00003_18101512:00:28$
DATA_TYPE : VARCHAR2
DATA_TYPE_MOD :
DATA_TYPE_OWNER :
DATA_LENGTH : 10
DATA_PRECISION :
DATA_SCALE :
NULLABLE : Y
COLUMN_ID :
DEFAULT_LENGTH :
DATA_DEFAULT :
NUM_DISTINCT :
LOW_VALUE :
HIGH_VALUE :
DENSITY :
NUM_NULLS :
NUM_BUCKETS :
LAST_ANALYZED :
SAMPLE_SIZE :
CHARACTER_SET_NAME : CHAR_CS
CHAR_COL_DECL_LENGTH : 10
GLOBAL_STATS : NO
USER_STATS : NO
AVG_COL_LEN :
CHAR_LENGTH : 10
CHAR_USED : B
V80_FMT_IMAGE : NO
DATA_UPGRADED : YES
HIDDEN_COLUMN : YES
VIRTUAL_COLUMN : NO
SEGMENT_COLUMN_ID : 3
INTERNAL_COLUMN_ID : 3
HISTOGRAM : NONE
QUALIFIED_COL_NAME : SYS_C00003_18101512:00:28$
USER_GENERATED : NO
DEFAULT_ON_NULL : NO
IDENTITY_COLUMN : NO
EVALUATION_EDITION :
UNUSABLE_BEFORE :
UNUSABLE_BEGINNING :
COLLATION : USING_NLS_COMP
COLLATED_COLUMN_ID :
PL/SQL procedure successfully completed.
SQL>