---free block pool自由块池我理解可能是undo segment中的空闲块的存储信息，因为undo segment也是循环使用的啊
FREE BLOCK POOL::
uba: 0x00800158.0046.3a ext: 0x4 spc: 0x302
uba: 0x00000000.0046.25 ext: 0x4 spc: 0x904
uba: 0x00000000.0043.14 ext: 0x1 spc: 0x13fe
uba: 0x00000000.0013.09 ext: 0x13 spc: 0x1b8c
uba: 0x00000000.0000.00 ext: 0x0 spc: 0x0
TRN TBL::
---事务表的条目，共计48条，可能不同数据库版本也会有差异,可见事务表条目也有scn
index state cflags wrap# uel scn dba parent-xid nub stmt_num cmt
------------------------------------------------------------------------------------------------
0x00 9 0x00 0x00b0 0x000a 0x0001.000009bb 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448957928
0x01 9 0x00 0x00ae 0x002d 0x0000.028f6419 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x02 9 0x00 0x00af 0x0023 0x0000.028f64b2 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x03 9 0x00 0x00af 0x0011 0x0001.00000197 0x00800157 0x0000.000.00000000 0x00000002 0x00000000 1448953786
0x04 9 0x00 0x00af 0x0027 0x0001.00000a36 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448957928
0x05 9 0x00 0x00ae 0x0017 0x0001.00000341 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x06 9 0x00 0x00af 0x0024 0x0001.00000417 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x07 9 0x00 0x00af 0x000c 0x0001.0000032e 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x08 9 0x00 0x00af 0x000f 0x0001.000007e6 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448956848
0x09 9 0x00 0x00ae 0x0005 0x0001.0000033b 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x0a 9 0x00 0x00af 0x0020 0x0001.000009da 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448957928
0x0b 9 0x00 0x00ae 0x0003 0x0001.0000017d 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448953725
0x0c 9 0x00 0x00ae 0x0029 0x0001.00000331 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x0d 9 0x00 0x00ae 0x002c 0x0001.000002a1 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x0e 9 0x00 0x00af 0x0018 0x0001.00000366 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x0f 9 0x00 0x00af 0x0000 0x0001.0000082d 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448956850
0x10 9 0x00 0x00af 0x0021 0x0001.00000d8c 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448960328
0x11 9 0x00 0x00ae 0x000d 0x0001.000001fd 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448953867
0x12 9 0x00 0x00ae 0x0019 0x0001.000003b0 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x13 9 0x00 0x00af 0x001e 0x0001.000003c4 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x14 9 0x00 0x00af 0x0012 0x0001.000003a8 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x15 9 0x00 0x00ae 0x0026 0x0001.000002f3 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x16 9 0x00 0x00af 0x0008 0x0001.000006ca 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448956127
0x17 9 0x00 0x00af 0x000e 0x0001.00000362 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x18 9 0x00 0x00af 0x001d 0x0001.0000036c 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x19 9 0x00 0x00af 0x0013 0x0001.000003c2 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1a 9 0x00 0x00ae 0x0016 0x0001.00000445 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1b 9 0x00 0x00af 0x002b 0x0001.000003f7 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1c 9 0x00 0x00af 0x002e 0x0001.000003de 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1d 9 0x00 0x00ae 0x002f 0x0001.00000384 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1e 9 0x00 0x00af 0x001c 0x0001.000003c8 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x1f 9 0x00 0x00aa 0x0002 0x0000.028f649e 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x20 9 0x00 0x00ae 0x0004 0x0001.00000a28 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448957928
0x21 9 0x00 0x00af 0x002a 0x0001.00000dad 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448960328
0x22 9 0x00 0x00ad 0x0028 0x0000.028f6482 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x23 9 0x00 0x00ae 0x000b 0x0001.00000083 0x00000000 0x0000.000.00000000 0x00000000 0x00000000 1448953127
0x24 9 0x00 0x00af 0x001a 0x0001.00000427 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x25 9 0x00 0x00ae 0x0007 0x0001.00000306 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x26 9 0x00 0x00ae 0x0025 0x0001.00000304 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x27 9 0x00 0x00af 0x0010 0x0001.00000a56 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448957928
0x28 9 0x00 0x00ae 0x001f 0x0000.028f6492 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x29 9 0x00 0x00ae 0x0009 0x0001.00000335 0x00800155 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x2a 9 0x00 0x00af 0xffff 0x0001.00000e73 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448960452
0x2b 9 0x00 0x00ae 0x0006 0x0001.00000401 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x2c 9 0x00 0x00ae 0x0015 0x0001.000002d2 0x00800157 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x2d 9 0x00 0x00ae 0x0022 0x0000.028f6466 0x00800156 0x0000.000.00000000 0x00000001 0x00000000 1448952168
0x2e 9 0x00 0x00af 0x001b 0x0001.000003e4 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
0x2f 9 0x00 0x00ae 0x0014 0x0001.000003a2 0x00800158 0x0000.000.00000000 0x00000001 0x00000000 1448954328
End dump data blocks tsn: 1 file#: 2 minblk 105 maxblk 105
[ora10g@seconary udump]$
可见undo segment header block在几个结构皆有scn,到底是哪个scn呢
要解决这个问题，就要去理解undo segment header block的原理及结构了
转换思路，我们看看trc文件有什么信息，或者说我们重要要关注哪些部分的信息