oracle数据文件内部BLOCK结构详解 datafile block block size :8192Offset 0 1 2 3 4 5 6 7 8 9 a b c d e f 00014000 06 A2 00 00 0A 00 40 01 0E 89 43 00 00 ......
Index to the first slot on the ITL freelist. ITL TX freelist slot
fnx :
自由列表中下一块的地址 Null if this block is not on a freelist 有数据例如: fnx: 0x1000029
00014030
50
18
00
00
96
14
80
00
B9
07
01
00
01
20
00
00
xid
uba
Lck Flag
Scn/Fsc
xid :
Transaction ID (UndoSeg.Slot.Wrap) 值可以用select XIDUSN, XIDSLOT,XIDSQN from v$transaction;查到 This is comprised of the rollback segment number (2 bytes), the slot number in the transaction table of that rollback segment (2 bytes), and the number of times use of that transaction table has wrapped (4 bytes).
uba :
Undo address (UndoDBA.SeqNo.RecordNo) The location of the undo for the most recent change to this block by this transaction. This is comprised of the DBA of the rollback segment block (4 bytes), the sequence number (2 bytes), and the record number for the change in that undo block (1 byte), plus 1 unused byte.
