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Block Dump

November 7th, 2006
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Block Dump究竟是从memory中读取还是从datafile 中读取？

最近一次有趣的讨论得到出以下的结论

alter system dump datafile file_id block block_number, 如果buffer中存在该block，将从buffer中读取

alter system dump datafile file_name block block_number ,不管buffer中是否存在，都将从文件中读取

通过truss来跟踪 truss -t open,close,read -p 24490
SQL> alter system dump datafile 4 block 2468;

System altered.
read(7, “01\v\0\006\0\0\0\0\011 i”.., 2064) = 267
read(7, 0x1037F3976, 2064) (sleeping…)


SQL> alter system dump datafile ‘/oracle/GBPGW/data01/CSHAN/CSHAN_system02a.dbf’ block 2468;

System altered.

Received signal #21, SIGURG, in read() [caught]
siginfo: SIGURG pid=24489 uid=32000
read(7, 0x1037F3976, 2064) Err#91 ERESTART
read(7, “\0\v\0\0\f\0\0\001\002″, 2064) = 11
read(7, “01 6\0\006\0\0\0\0\011 i”.., 2064) = 310
open(“/oracle/GBPGW/data01/CSHAN/CSHAN_system02a.dbf”, O_RDONLY) = 11
read(11, “\002\0\0\0\0 \0\0\0 d\0″.., 512) = 512
close(11) = 0
open(“/oracle/GBPGW/data01/CSHAN/CSHAN_system02a.dbf”, O_RDWR) = 11
close(11) = 0
open(“/oracle/GBPGW/data01/CSHAN/CSHAN_system02a.dbf”, O_RDONLY) = 11
close(11) = 0
close(259) = 0
read(7, 0x1037F3976, 2064) (sleeping…)

Eagle Fan oracle

  1. www
    November 8th, 2006 at 17:57 | #1
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    以前从来没考虑过这个问题。
    这样看来，某些时刻，两个结果有不一致的可能？

    truss是好东西。

  2. Eagle Fan
    November 9th, 2006 at 12:37 | #2
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    是的，我新建了一个表，从dump中来看
    dump datafile ‘file_name’ block xxx
    显示是leaf block
    dump datafile ‘file_id’ block xxxx
    显示是data block

    Leaf block dump
    ===============
    header address 4353484892=0x1037ce85c
    kdxcolev 0
    KDXCOLEV Flags = – - -
    kdxcolok 0
    kdxcoopc 0×80: opcode=0: iot flags=— is converted=Y
    kdxconco 3
    kdxcosdc 0
    kdxconro 0
    kdxcofbo 36=0×24
    kdxcofeo 8032=0x1f60
    kdxcoavs 7996
    kdxlespl 0
    kdxlende 0
    kdxlenxt 0=0×0
    kdxleprv 0=0×0
    kdxledsz 0
    kdxlebksz 8032
    —– end of leaf block dump —–
    End dump data block from file /oracle/GBPGW/data01/CSHAN/CSHAN_system02a.dbf minblk 2461 maxblk 2461
    Start dump data blocks tsn: 0 file#: 4 minblk 2461 maxblk 2461
    buffer tsn: 0 rdba: 0x0100099d (4/2461)
    scn: 0×0000.00561b42 seq: 0×01 flg: 0×00 tail: 0x1b420601
    frmt: 0×02 chkval: 0×0000 type: 0×06=trans data
    Block header dump: 0x0100099d
    Object id on Block? Y
    seg/obj: 0×2243 csc: 0×00.561869 itc: 2 flg: O typ: 1 – DATA
    fsl: 0 fnx: 0×0 ver: 0×01

    Itl Xid Uba Flag Lck Scn/Fsc
    0×01 0×0002.040.00003976 0x00c00fb5.1afb.06 C— 0 scn 0×0000.005616ea
    0×02 0×0002.03d.00003980 0x00c01014.1afc.4a —- 1 fsc 0×0000.00000000

    data_block_dump,data header at 0x1037ce85c
    ===============
    tsiz: 0x1fa0
    hsiz: 0×14
    pbl: 0x1037ce85c
    bdba: 0x0100099d
    76543210
    flag=——–
    ntab=1
    nrow=1
    frre=-1
    fsbo=0×14
    fseo=0x13df
    avsp=0x1f83
    tosp=0x1f83
    0xe:pti[0] nrow=1 offs=0
    0×12:pri[0] offs=0x13df
    block_row_dump:

    alter system checkpoint后就都一样了

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