通过bbed查看数据块结构

本文转自：http://www.xifenfei.com/1524.html

BBED> map /v
 File: /opt/oracle/oradata/xifenfei/xff01.dbf (2)
 Block: 530                                   Dba:0x00800212
------------------------------------------------------------
 KTB Data Block (Table/Cluster)
 
 struct kcbh, 20 bytes                      @0       
    ub1 type_kcbh                           @0       
    ub1 frmt_kcbh                           @1       
    ub1 spare1_kcbh                         @2       
    ub1 spare2_kcbh                         @3       
    ub4 rdba_kcbh                           @4       
    ub4 bas_kcbh                            @8       
    ub2 wrp_kcbh                            @12      
    ub1 seq_kcbh                            @14      
    ub1 flg_kcbh                            @15      
    ub2 chkval_kcbh                         @16      
    ub2 spare3_kcbh                         @18      
 
 struct ktbbh, 72 bytes                     @20      
    ub1 ktbbhtyp                            @20      
    union ktbbhsid, 4 bytes                 @24      
    struct ktbbhcsc, 8 bytes                @28      
    b2 ktbbhict                             @36      
    ub1 ktbbhflg                            @38      
    ub1 ktbbhfsl                            @39      
    ub4 ktbbhfnx                            @40      
    struct ktbbhitl[2], 48 bytes            @44      
 
 struct kdbh, 14 bytes                      @92      
    ub1 kdbhflag                            @92      
    b1 kdbhntab                             @93      
    b2 kdbhnrow                             @94      
    sb2 kdbhfrre                            @96      
    sb2 kdbhfsbo                            @98      
    sb2 kdbhfseo                            @100     
    b2 kdbhavsp                             @102     
    b2 kdbhtosp                             @104     
 
 struct kdbt[1], 4 bytes                    @106     
    b2 kdbtoffs                             @106     
    b2 kdbtnrow                             @108     
 
 sb2 kdbr[101]                              @110     
 
 ub1 freespace[4270]                        @312     
 
 ub1 rowdata[3606]                          @4582    
 
 ub4 tailchk                                @8188    
 
 
BBED> 
 
 
////////////////////////////////////////////////////////////////////////////////////////
//////////// Block Header Structure,  20 bytes//////////////////////////////////////////
BBED> p kcbh
struct kcbh, 20 bytes                       @0       
    ub1 type_kcbh                           @0    -- Block Type 
                                                  -- 01 - Undo segment header
                                                  -- 02 - Undo data block
                                                  -- 03 - Save undo header
                                                  -- 04 - Save undo data block
                                                  -- 05 - Data segment header  
                                                  -- 06 - Trans data, KTB managed data block(with ITL)
                                                  -- 07 - Temp table data block (no ITL)
                                                  -- 08 - Sort key
                                                  -- 09 - Sort Run
                                                  -- 10 - Segment free list block
                                                  -- 11 - Data file header
    ub1 frmt_kcbh                           @1    -- Block Format 1=Oracle7, 2=Oracle8+   
    ub1 spare1_kcbh                         @2    -- Not used, filler field   
    ub1 spare2_kcbh                         @3    -- Not used, filler field   
    ub4 rdba_kcbh                           @4    -- RDBA (4 bytes) - Relative Data Block Address   
    ub4 bas_kcbh                            @8    -- SCN Base (4 bytes)  
    ub2 wrp_kcbh                            @12   -- SCN Wrap (2 bytes)   
    ub1 seq_kcbh                            @14   -- Sequence Number, incremented for every change made to the block at the same SCN    
    ub1 flg_kcbh                            @15   -- Flag:   
                                                  -- 0x01 New Block
                                                  -- 0x02 Delayed Logging Chang advanced SCN/seq
                                                  -- 0x04 Check value saved - block XOR's to Zero
                                                  -- 0x08 Temporary block
    ub2 chkval_kcbh                         @16   -- Optional block checksum (if DB_BLOCK_CHECKSUM=TRUE)   
    ub2 spare3_kcbh                         @18   -- Not used, filler field  
  
 /////////////////////////////////////////////////////////////////////////////////////////
/////////Transaction Fixed Header Structure, 72 Bytes////////////////////////////////////
BBED> p ktbbh
 struct ktbbh, 72 bytes                     @20      
    ub1 ktbbhtyp                            @20     -- Block type (1=DATA, 2=INDEX) 
    union ktbbhsid, 4 bytes                 @24     -- Segment/Object ID
    struct ktbbhcsc, 8 bytes                @28     -- SCN at last block cleanout 
    b2 ktbbhict                             @36     -- Number of ITL slots 
    ub1 ktbbhflg                            @38     -- 0=on the freelist 
    ub1 ktbbhfsl                            @39     -- ITL TX freelist slot 
    ub4 ktbbhfnx                            @40     -- DBA of next block on the freelist 
    struct ktbbhitl[2], 48 bytes            @44     -- ITL list index, each ITL takes up 24 bytes 
 
//////////////////////////////////////////////////////////////////////////////////////////
///////////////Data Header Structure, 14 bytes////////////////////////////////////////////
BBED> p kdbh
 struct kdbh, 14 bytes                      @100     
    ub1 kdbhflag                            @100    -- N=pctfree hit(clusters)
                                                    -- F=do not put on freelist
                                                    -- K=flushable cluster keys 
    b1 kdbhntab                             @101    -- Number of tables (>1 in clusters) 
    b2 kdbhnrow                             @102    -- Number of rows (2 bytes)
    sb2 kdbhfrre                            @104    -- First free row entry index; -1=you have to add one 
    sb2 kdbhfsbo                            @106    -- Freespace begin offset 
    sb2 kdbhfseo                            @108    -- Freespace end offset 
    b2 kdbhavsp                             @110    -- Available space in the block 
    b2 kdbhtosp                             @112    -- Total available space when all TXs commit 
 
////////////////////////////////////////////////////////////////////////////////////////
/////////////////////Table Directory Entry Structure, 4 bytes///////////////////////////
BBED> p kdbt
 struct kdbt[1], 4 bytes                    @114     
    b2 kdbtoffs                             @114     
    b2 kdbtnrow                             @116     
 
////////////////////////////////////////////////////////////////////////////////////////
////////////////// Row Directory ///////////////////////////////////////////////////////
BBED> p kdbr[100]
 sb2 kdbr[100]                                @310     
 
 
////////////////////////////////////////////////////////////////////////////////////////
///////////////// Free Space ///////////////////////////////////////////////////////////
BBED> p freespace[4269]
 ub1 freespace[4269]                        @4581     
 
///////////////////////////////////////////////////////////////////////////////////////
/////////////////////Row Data//////////////////////////////////////////////////////////
BBED> p rowdata[3605]
ub1 rowdata[3605]                           @8187     0x00   
  
//////////////////////////////////////////////////////////////////////////////////////
/////////////////////Block Tail Check, 4 bytes////////////////////////////////////////
BBED> p tailchk
ub4 tailchk                                 @8188     0x24500601

说明事宜：
1、tailchk=Lower order two bytes of SCN Base(bas_kcbh) + Block Type(type_kcbh) + SCN Seq(seq_kcbh)
2、块的scn为：scn=wrp_kcbh+bas_kcbh
求scn语句：select to_char(to_number(‘scn’,'xxxxxxxxxx’),’999999999999′) from dual;
3、dba求文件号，块号为：

set serveroutput on
declare
   p_dba   VARCHAR2 (255) :='0x00800212';
   l_str   VARCHAR2 (255) DEFAULT NULL;
BEGIN
    l_str :=
         'datafile# is:'
      || DBMS_UTILITY.data_block_address_file (TO_NUMBER (LTRIM (p_dba, '0x'),'xxxxxxxx'))
      || chr(10)||'datablock is:'
      || DBMS_UTILITY.data_block_address_block (TO_NUMBER (LTRIM (p_dba, '0x'),'xxxxxxxx'));
   dbms_output.put_line(l_str);
END;