Blockdump - 8.x Data Segment Header in Oracle

Subject:  QREF: Blockdump - 8.x Data Segment Header in Oracle 

Creation Date:  25-APR-2000 





CACHE BLOCK:

See Note: 47132.1

     type: 0x10=DATA SEGMENT HEADER - UNLIMITED



EXTENT CONTROL:

  Extent Header:: spare1: 0      space2: 0      #extents: 13     #blocks: 1429  

                  last map  0x00000000  #maps: 0      offset: 4128  

      Highwater::  0x020004d0  ext#: 12     blk#: 275    ext size: 475   

  #blocks in seg. hdr's freelists: 5     

  #blocks below: 1229  

  mapblk  0x00000000  offset: 12    

                   Unlocked

==> spare1:   this field is no longer used (old inc#, now always 0)

==> space2:   this field is no longer used (old ts#, now always 0)

==> #extents: number of extents allocated to segment

==> #blocks:  number of blocks allocated to segment



==> last map: address of last extent map block

              0 if extent map is entirely in the segment header

==> #maps:    number of extent map block

==> offset:   offset to end of extent map



==> HWM dba:  address of block at highwater mark

==> ext#:     HWM extent number relative to segment

==> blk#:     HWM block number within extent

==> ext size: HWM extent size (in blocks)

==> #blocks in seg. hdr's freelists: number of blocks in seg. hdr's free list 

==> #blocks below: number of blocks below HWM

==> mapblk dba: dba of extent map block containing HWM extent

                is 0 if HWM is in the segment header

==> offset:   offset within extent map block

              is the ext# if HWM is in segment header



==> Locked by: if locked by a transaction, the xid is displayed





EXTENT MAP:

Map Header:: next  0x00000000  #extents: 13   obj#: 12141  flag: 0x40000000

   0x02000003  length: 4     

   0x02000007  length: 5     

   0x0200000c  length: 10    

   0x02000016  length: 15    

   0x02000025  length: 20    

   0x02000039  length: 30    

   0x02000057  length: 45    

   0x02000084  length: 65    

   0x020000c5  length: 95    

   0x02000124  length: 140   

   0x020001b0  length: 210   

   0x02000282  length: 315   

   0x020003bd  length: 475   

Map Header:

==> next dba: address of next extent map block

==> #extents: number of extents in this extent map block

==> obj#:     object id for this segment

==> flag:     Flag to mark the version of segment header

              is 2 if the segment header is V8

Map Extent:

==> dba:      dba of extent

==> length:   number of blocks in extent





FREE LIST:

  nfl = 1, nfb = 1 typ = 1 nxf = 0

  SEG LST:: flg: USED   lhd: 0x020004cb ltl: 0x020004cf 

Segment Header:

==> nfl: number of free lists/block

==> nfb: number of free list blocks + segment header

==> typ: block type 

==> nxf: number of transaction free lists

Segment List:

==> flg: flag USED or UNUSED the free list

==> lhd: head of free list

==> ltl: tail of free list