How does Oracle fills the Blocks of an extent ?

Hi,
does anybody know why Oracle uses p.e. the fourth block of the first extent, then the 8th block, and not continous amount of blocks?
So the HWM is higher then necessary.
Thanks
Marco

Thanks Mark for the fast Reply.
Yes, you are right, seeing is beliving ... :-)
I had imported a table into the db (and there were NO deletes!)
SQL> select tablespace_name, initial_extent, ALLOCATION_TYPE, SEGMENT_SPACE_MANAGEMENT from dba_tablespaces where tablespace_name='KUNDEN';
TABLESPACE_NAME INITIAL_EXTENT ALLOCATIO SEGMEN
KUNDEN 5242880 UNIFORM AUTO
SQL> select count(*) from orte;
COUNT(*)
1628
SQL> select segment_name, tablespace_name, header_block, bytes, blocks, extents from dba_segments where segment_name='ORTE';
SEGMENT_NAME TABLESPACE_NAME HEADER_BLOCK BYTES BLOCKS EXTENTS
ORTE KUNDEN 28820 5242880
640 1
SQL> SELECT DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) AS block_nr, COUNT(*) AS anzahl FROM orte
GROUP BY DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID)
BLOCK_ID ROWS_IN_BLOCK
28844 255
28848 218
28852 230
28856 233
28864 241
28860 244
28868 207
Thanks
Marco

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user10541890 wrote:
How does oracle 10g execute a correlated subquery?
I read some articles online & i am a little confused.
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