blocks,extents,segments

<pre name="code" class="sql"><pre name="code" class="sql">Block: Oracle存储的最小单位Extent：EXTENT_IDNUMBER Extent number in the segmentBLOCK_IDNUMBER Starting block number of the extentBLOCKSNUMBER Size of the extent in Oracle blockSQL> set linesize 200SQL> select owner,segment_name,extent_id,file_id,block_id,blocks from dba_extents  where owner='TEST' and segment_name='BFW_TEST';OWNER       SEGMENT_NAME  EXTENT_ID    FILE_ID BLOCK_ID     BLOCKS------------------------------ --------------------------------------------------------------------------------- ---------- ---------- ---------- ----------TEST       BFW_TEST   0     6     5376 128TEST       BFW_TEST   1     6     1792 128TEST       BFW_TEST   2     6     1920 128TEST       BFW_TEST   3     6     2048 128TEST       BFW_TEST   4     6     2176 128TEST       BFW_TEST   5     6     3712 128TEST       BFW_TEST   6     6     3840 128TEST       BFW_TEST   7     6     3968 128TEST       BFW_TEST   8     6     4096 128已选择9行。select owner,segment_name,header_file,header_block,blocks,extents from dba_segments where owner='TEST' and segment_name='BFW_TEST'SQL> SQL> ;OWNER       SEGMENT_NAME HEADER_FILE HEADER_BLOCK     BLOCKSEXTENTS------------------------------ --------------------------------------------------------------------------------- ----------- ------------ ---------- ----------TEST       BFW_TEST    6     53761152      9HEADER_FILENUMBER ID of the file containing the segment headerHEADER_BLOCKNUMBER ID of the block containing the segment headerBLOCKSNUMBER Size, in Oracle blocks, of the segment  --segment的块数 = 128 * 9EXTENTSNUMBER Number of extents allocated to the segmentSQL> select owner,segment_name,extent_id,file_id,block_id,blocks from dba_extents  where owner='TEST' and segment_name='TEST';OWNER       SEGMENT_NAME  EXTENT_ID    FILE_ID BLOCK_ID     BLOCKS------------------------------ --------------------------------------------------------------------------------- ---------- ---------- ---------- ----------TEST       TEST  0    10    15232 128TEST       TEST  1     6    18432 128TEST       TEST  2    10    15360 128TEST       TEST  3     6    19200 128TEST       TEST  4    10    15488 128TEST       TEST  5     6    19328 128TEST       TEST  6    10    15616 128TEST       TEST  7     6    19456 128TEST       TEST  8    10    15744 128但是segment上的block不一定连续,extent 不能跨数据文件(因为extent都是连续的block)segment不可以跨表空间但可以跨数据文件