segments의 소유자와 segments의 이름, 유형, tablespace 이름, extent, parameter 설정등의 정보를 담고 있다.
【예제】
SQL> desc dba_segments;
Name Null? Type
----------------------------------------- -------- ----------------------------
OWNER VARCHAR2(30)
SEGMENT_NAME VARCHAR2(81)
PARTITION_NAME VARCHAR2(30)
SEGMENT_TYPE VARCHAR2(18)
TABLESPACE_NAME VARCHAR2(30)
HEADER_FILE NUMBER
HEADER_BLOCK NUMBER
BYTES NUMBER
BLOCKS NUMBER
EXTENTS NUMBER
INITIAL_EXTENT NUMBER
NEXT_EXTENT NUMBER
MIN_EXTENTS NUMBER
MAX_EXTENTS NUMBER
PCT_INCREASE NUMBER
FREELISTS NUMBER
FREELIST_GROUPS NUMBER
RELATIVE_FNO NUMBER
BUFFER_POOL VARCHAR2(7)
SQL> select tablespace_name, count(*) segments, sum(bytes) bytes
2 from dba_segments
3 group by tablespace_name;
TABLESPACE_NAME SEGMENTS BYTES
------------------------------ ---------- ----------
SYSAUX 3178 319094784
SYSTEM 1147 462028800
UNDOTBS1 10 4587520
USERS 9 589824
SQL>