oracle deep internal 1 (ver.2)

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Ver.2(2016.07.18)

© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved.2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis

It's so difficult to understand only through the book.I'd like to check internal actual situation of oracle

with my own eyes

"Undo" mechanism as explained in Jonathan Lewis's book


2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis

UPDATE Table A SET col1 = ‘B’

AA

Redolog

undo

DataFile

AB

A

B

Simple flow chart in oracle when processing Update statement

SGA

Undo Segment

Shared Pool Buffer Cache


Data Block

v$transaction

Undo Headerindex state cflags wrap# uel scn dba---------------------------------------------------------------------------------------------------------------------

0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000

Undo Block

ITL

Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000

Rowsblock_row_dump:tab 0, row 0, @0x1f88tl: 16 fb: --H-FL-- lb: 0x1 cc: 2col 0: [10] 31 20 20 20 20 20 20 20 20 20col 1: [ 1] 41 ASCII HEXA code 41

=> Value ‘A’

* Rec #0x1

BH

1. Initial state when a value of "A" is entered (The first stage before update)

SGA

Undo Segment



Data Block

v$transaction

ITL


Rowsblock_row_dump:tab 0, row 0, @0x1f88tl: 16 fb: --H-FL-- lb: 0x1 cc: 2col 0: [10] 31 20 20 20 20 20 20 20 20 20col 1: [ 1] 41

Undo Headerindex state cflags wrap# uel scn dba---------------------------------------------------------------------------------------------------------------------


Undo Block

* Rec #0x1

BH

BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2col 0: [10] 31 20 20 20 20 20 20 20 20 20col 1: [ 1] 41

UPDATE Table A

SET col1 = ‘B’

ASCII HEXA code 41=> Value ‘A’

(The preparation stage before update)

1_1. State in which generating CU Block into Buffer Cache by selecting one from DB block

SGA

Undo Segment



Data Block

BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41

BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41

CR

ITL



Undo Headerindex state cflags wrap# uel scn dba----------------------------------------------------------------------------------------------------------------


v$transactionBH‘a438’XCU block is copied to BH‘a1c8’XCU block

BH‘a438’block is changed from XCU to CR

0x643fa1c8

Undo Block

* Rec #0x1

BH


copy XCU block

change from XCU to CR

0x643fa438

2. When executing Update statement, generates new CU block in Buffer Cache and changes from CU block to CR block

SGA

Undo Segment



Data Block

BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000st: CR md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41

ITL



Undo Headerindex state cflags wrap# uel scn dba---------------------------------------------------------------------------------------------------------------


V$transaction

XID_INFO UBA_INFO TXN_INFO-------------- --------------- ------------------------------addr : status : IDLExidusn : ubafil : start_date : 2015-12-10 10:52:46xidslot : ubablk : ses_addr : 000000006B21CC20xidsqn : ubasqn :

0000000069B01FB0


For processing TX, Address is allocated in v$transaction data at the very first

Undo Block

* Rec #0x1

BH


2_1. Address data is generated in v$transaction. (Allocating memory about Row Cache new tx)

SGA

Undo Segment



Data Block

V$transaction


ITL



=> Value ‘A’



Undo Block

* Rec #0x1

BH


BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 410000000069B01FB0

7

After allocating address,

USN(Undo Segment Number) is

registered in v$transaction data

for the second time

Undo Segment

Number

3. Xid usn's value is allocated in v$transaction. (No. 7 usn in here)

SGA

Undo Segment



Data Block

V$transaction


0000000069B01FB0

7Undo Segment Number



ITL



=> Value ‘A’



Undo Block

* Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: Noncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41

BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0

10 0x80 0x04ed 0x0000 0x0000.003dbe4d

Undo slot

active0x018000a2

Undo Block Address

Before image value ‘A’

4. In Undo segment, Slot value is changed from 9 to 10

SGA

Undo Segment



Data Block

V$transaction


0000000069B01FB0

7Undo Segment Number

ITL



=> Value ‘A’



Undo Block



Undo Block Address


10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2


BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41tl: 16 fb: --H-FL-- lb: 0x2 cc: 2

0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000

col 1: [ 1] 42

Update ‘A’ to ‘B’ of CU block

CleanOut: itl No.1 change (--U- C---)Txn data change: itl No.2 change (Xid,Uba)Lock Byte change: 0x1 0x2

Undo slot active

5. Update value A to B of XCU block in Buffer Cache

SGA

Undo Segment



Data Block



Undo Block



Undo Block Address


10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2

ITL



=> Value ‘A’

V$transaction



BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42

7

0000000069B01FB0

1

1261

162

ACTIVE

6

469

Registered with the order as below in v$transaction.* addr ⟶ xidusn ⟶ xidslot, xidsqn, ubablk

Undo slot active

6. Allocate into other column except xid and uba in v$transaction

SGA

Undo Segment



Data Block

V$transaction


ITL



=> Value ‘A’



--U- 1 fsc 0x0000.003dbe4e



Undo Block



Undo Block Address


Undo slot active

10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2

Allocating equal scn to Itl slot and undo header slot

COMMIT ;

7. Commit execute (Allocating equal scn to Itl slot and undo header slot)

After commit, TX data is deleted in v$transaction

SGA

Undo Segment



Data Block

V$transaction




ITL



tl: 16 fb: --H-FL-- lb: 0x2 cc: 2col 0: [10] 31 20 20 20 20 20 20 20 20 20col 1: [ 1] 42

0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e

Value 'B' reflects Data block



Undo Block



Undo Block Address


Undo slot active

10 0x80 0x04ed 0x0000 0x018000a20x0000.003dbe4e

BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4etl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42

Checkpoint ;

8. Executing Check point (CU block reflects disk block)

SGA

Undo Segment



Data Block


BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4etl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42

V$transaction


ITL

Itl Xid Uba Flag Lck Scn/Fsc0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e



0x00 10 0x80 0x04ed 0x0000 0x0000.003dbe4e 0x018000a20x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000

Undo Block



Undo Block Address


Undo slot active

Summary : DML Operation in a Data Block

Oracle Deep Internal

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oracle deep internal 1 (ver.2)

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