Oracle Study之案例--Oracle ASSM管理方式下的BITMAP

OracleStudy之案例--OracleASSM管理方式下的Bitmap在基于此在LMT(ExtentLocalManagement）下Oracle建议我们使用ASSM（AutomaticSegment-SpaceManagement），看看

Oracle Study之案例--Oracle ASSM管理方式下的Bitmap

     在基于此在LMT(Extent Local Management）下Oracle建议我们使用ASSM（Automatic Segment-Space Management），看看

Oracle doc是如何来解释ASSM的：

      This keyword tells Oracle that you want to use bitmaps to manage the free space with in segments. A bitmap, in this case, is a map that describes the status of each data block within a segment with respect to the amount of space in the block available for inserting rows. As more or less space becomes available in a data block, its new state is reflected in  the bitmap. Bitmaps enable Oracle to manage free space more automatically; thus, this form  of space management is called automatic segment-space management. Locally managed tablespaces using automatic segment-space management can be created as  smallfile (traditional) or bigfile tablespaces. AUTO is the default.

案例分析：

1、查看emp表存储信息

17:31:39 SYS@ test1 >col segment_name for a20 17:33:01 SYS@ test1 >select owner,segment_name,segment_type,tablespace_name,bytes/1024 from dba_segments 17:33:24   2   where segment_name='EMP'; OWNER                          SEGMENT_NAME         SEGMENT_TYPE       TABLESPACE_NAME                BYTES/1024 ------------------------------ -------------------- ------------------ ------------------------------ ---------- SCOTT                          EMP                  TABLE              USERS                                   64 17:31:06 SYS@ test1 >select tablespace_name,contents,extent_management,SEGMENT_SPACE_MANAGEMENT from dba_tablespaces; TABLESPACE_NAME                CONTENTS  EXTENT_MAN SEGMEN ------------------------------ --------- ---------- ------ SYSTEM                         PERMANENT DICTIONARY MANUAL USERS                            PERMANENT LOCAL      AUTO 17:37:42 SYS@ test1 >COL OWNER FOR A10 17:37:54 SYS@ test1 >R   1  select owner,SEGMENT_NAME,EXTENT_ID, FILE_ID,BLOCK_ID,BLOCKS from dba_extents   2*  where segment_name='EMP' OWNER      SEGMENT_NAME                                        EXTENT_ID    FILE_ID   BLOCK_ID     BLOCKS ---------- -------------------------------------------------- ---------- ---------- ---------- ---------- SCOTT      EMP                                                         0          4        144          8 17:16:05 SYS@ test1 >select header_file,header_block,blocks,extents from dba_segments where segment_name='EMP'; HEADER_FILE HEADER_BLOCK     BLOCKS    EXTENTS ----------- ------------ ---------- ----------           4          146          8          1

2、对emp表中的block进行dump分析

17:39:30 SYS@ test1 >alter system dump datafile 4 block min 144 block max 151;

System altered.

查看dump的trace文件：

[oracle@RH6 ~]$ ls -lt /u01/app/oracle/diag/rdbms/test1/test1/trace/|more

total 56908

-rw-r----- 1 oracle oinstall    25923 Dec 15 17:42 test1_ora_2385.trc