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 a2017:33:01 sys@ test1 >select owner,segment_name,segment_type,tablespace_name,bytes/1024 from dba_segments17:33:24 2 where segment_name='emp';owner segment_name segment_type tablespace_name bytes/1024------------------------------ -------------------- ------------------ ------------------------------ ----------scott emp table users 6417:31:06 sys@ test1 >select tablespace_name,contents,extent_management,segment_space_management from dba_tablespaces;tablespace_name contents extent_man segmen------------------------------ --------- ---------- ------system permanent dictionary manualusers permanent local auto17:37:42 sys@ test1 >col owner for a1017:37:54 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 4 144 817:16:05 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