Shulou(Shulou.com)06/01 Report--

There are two main types of Oracle data blocks: file header blocks and data blocks. Let's first introduce the data block: the data block is simply divided into the following layers:

BBED > set dba 1mai 58914 DBA 0x0040e622 (4253218 1m 58914) BBED > map File: / u01/app/oracle/oradata/qxptfh01/system01.dbf (1) Block: 58914 Dba:0x0040e622 -KTB Data Block (Table/Cluster) struct kcbh 20 bytes @ 0-Cache Layer-struct ktbbh, 72 bytes @ 20-Transaction Layer-struct kdbh, 14 bytes @ 92-Data Header-struct kdbt [1] 4 bytes @ 106-- Table Directory-sb2 kdbr [3] @ 110-Row Directory-ub1 freespace [8041] @ 116-Free Space-ub1 rowdata [31] @ 8157-Row Data-ub4 tailchk @ 8188-- Tailchk-

The part from Data header to Row Data is called Data Layer.

The first part of the Cache Layer:Block, which is 20 bytes long, has an internal data structure called kcbh, including

The following parts

BBED > p kcbhstruct kcbh, 20 bytes @ 0 ub1 type_kcbh @ 0 0x06-- Block type (table/index,rollback segment,temporary segment, etc.) ub1 frmt_kcbh @ 1 0xa2-- Block format (v6 Jing v7 V8) ub1 spare1_kcbh @ 2 0x00-keep ub1 spare2_kcbh @ 3 0x00-retain ub4 rdba_kcbh @ 4 0x0040e622-block address DBA ub4 bas_kcbh @ 8 0x01a9b470-- scn base ub2 Wrp_kcbh @ 12 0x0000-- scn wrap ub1 seq_kcbh @ 14 0x07-- Serial number of the block Set to 0xff, it is considered a bad block. Ub1 flg_kcbh @ 15 0x06 (KCBHFDLC, KCBHFCKV)-- the flag of the block, that is, the attribute of the block. Ub2 chkval_kcbh @ 16 0x153c-- check value, db_block_checksum=true, to have a value. Ub2 spare3_kcbh @ 18 0x0000-keep

Flg_kcbh:

Define KCBHFNEW 0 × 01 / * new block-zeroed data area * /

# define KCBHFDLC 0x02 / * Delayed Logging Change advance SCN/seq * /

# define KCBHFCKV 0 × 04 / * ChecK Value saved-block xor's to zero * /

# define KCBHFTMP 0 × 08 / * Temporary block * /

This is a value that can be combined, that is to say, when there is a promising 6, it is a combination of 2 and 4.

Type_kcbh:

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