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[ODI] chapter1 When Update statement is executed, How does oracle undo work?

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When Update statement is executed, How does oracle undo work?

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Oracle Deep Internal report no. 001 When Update statement is executed, How does oracle undo work? Research & Contents Team
When Update statement is executed, How does oracle undo work? 01 Lee Kun Oh (이근오) kolee@nate.com Kwon Kon Woo (권건우) redpine@ex-em.com
2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis "Undo" mechanism as explained in Jonathan Lewis's book It's so difficult to understand only through the book. I'd like to check internal actual situation of oracle with my own eyes
Simple flow chart in oracle when processing Update statement 2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis UPDATE Table A SET col1 = ‘B’ AA Redo log undo Data File AB A B
SGA Undo SegmentData Block Shared Pool Buffer Cache 1. Initial state when a value of "A" is entered (The first stage before update) v$transaction Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ * Rec #0x1 BH
SGA Undo SegmentData Block Shared Pool Buffer Cache 1_1. State in which generating CU Block into Buffer Cache by selecting one from DB block (The preparation stage before update) v$transaction Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 * Rec #0x1 BH ASCII HEXA code 41 => Value ‘A’ BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 UPDATE Table A SET col1 = ‘B’
SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 2.. When executing Update statement, generates new CU block in Buffer Cache and changes from CU block to CR block v$transaction CR ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 BH copy XCU block change from XCU to CR BH‘a438’XCU block is copied to BH‘a1c8’XCU block BH‘a438’block is changed from XCU to CR 0x643fa438 0x643fa1c8
SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 2_1. Address data is generated in v$transaction. (Allocating memory about Row Cache new tx) CR ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 BH V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 For processing TX, Address is allocated in v$transaction data at the very first
SGA Undo SegmentData Block Shared Pool Buffer Cache 3. Xidusn's value is allocated in v$transaction. (No. 7 usn in here) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 BH V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 After allocating address, USN(Undo Segment Number) is registered in v$transaction data for the second time Undo Segment Number
SGA Undo SegmentData Block Shared Pool Buffer Cache Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 4. In Undo segment, Slot value is changed from 9 to 10 Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Block Address 10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2 Undo slot active V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 Undo Segment Number
SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 5. Update value A to B of XCU block in Buffer Cache ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Undo slot active V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 CR Update ‘A’ to ‘B’ of CU block CleanOut : Itl No.1 change (--U-  C---) Txn data change: Itl No.2 change (Xid,Uba) Lock Byte change: 0x1  0x2 Undo Segment Number
SGA Undo SegmentData Block Shared Pool Buffer Cache V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : 0000000069B01FB0 status : IDLE xidusn : 7 ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 6. Allocate into other column except xid and uba in v$transaction ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 0x018000a2 7 0000000069B01FB0 1 1261 162 ACTIVE Undo Block Address Before image value ‘A’ Undo slot active 6 469 10 0x80 0x04ed 0x0000 0x0000.003dbe4d BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Registered with the order as below in v$transaction. * addr->xidusn-> xidslot, xidsqn, ubablk
SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 10 0x80 0x04ed 0x0000 0x0000.003dbe4d BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 7. Commit execute (Allocating equal scn to Itl slot and undo header slot) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a20x0000.003dbe4e --U- 1 fsc 0x0000.003dbe4e Undo slot active Allocating equal scn to Itl slot and undo header slot V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : After commit, TX data is deleted in v$transaction Commit;
SGA Undo SegmentData Block Shared Pool Buffer Cache 8. Executing Check point (CU block reflects disk block) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a2 tl: 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 Value 'B' reflects Data block 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e Undo slot active BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 10 0x80 0x04ed 0x0000 0x0000.003dbe4d0x0000.003dbe4e V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : Check Point;
SGA Undo SegmentData Block Shared Pool Buffer Cache ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e Summary : DML Operation in a Data Block Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a2 Undo slot active BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 10 0x80 0x04ed 0x0000 0x0000.003dbe4d0x0000.003dbe4e Value 'B' reflects Data block V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn :
Oracle Deep Internal More information https://youtu.be/s304cY8-IjMYouku Blog Video E-mail NAVER http://cafe.naver.com/playexem ITPUB http://blog.itpub.net/31135309/ Wordpress https://playexem.wordpress.com/ Youtube https://www.youtube.com/channel/ UC5wKR_-A0eL_Pn_EMzoauJg playexem@ex-em.com playexem@naver.com For more information, or to schedule an on-site education, contact via blog or e-mail Kon Woo, Kwon Kun Oh, Lee Sook jin, Kim Dae Deok, Lee

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[ODI] chapter1 When Update statement is executed, How does oracle undo work?

  • 1. Oracle Deep Internal report no. 001 When Update statement is executed, How does oracle undo work? Research & Contents Team
  • 2. When Update statement is executed, How does oracle undo work? 01 Lee Kun Oh (이근오) kolee@nate.com Kwon Kon Woo (권건우) redpine@ex-em.com
  • 3. 2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis "Undo" mechanism as explained in Jonathan Lewis's book It's so difficult to understand only through the book. I'd like to check internal actual situation of oracle with my own eyes
  • 4. Simple flow chart in oracle when processing Update statement 2011, Oracle Core Essential Internals for DBAs and Developers, Jonathan Lewis UPDATE Table A SET col1 = ‘B’ AA Redo log undo Data File AB A B
  • 5. SGA Undo SegmentData Block Shared Pool Buffer Cache 1. Initial state when a value of "A" is entered (The first stage before update) v$transaction Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ * Rec #0x1 BH
  • 6. SGA Undo SegmentData Block Shared Pool Buffer Cache 1_1. State in which generating CU Block into Buffer Cache by selecting one from DB block (The preparation stage before update) v$transaction Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 * Rec #0x1 BH ASCII HEXA code 41 => Value ‘A’ BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 UPDATE Table A SET col1 = ‘B’
  • 7. SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 2.. When executing Update statement, generates new CU block in Buffer Cache and changes from CU block to CR block v$transaction CR ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 BH copy XCU block change from XCU to CR BH‘a438’XCU block is copied to BH‘a1c8’XCU block BH‘a438’block is changed from XCU to CR 0x643fa438 0x643fa1c8
  • 8. SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 2_1. Address data is generated in v$transaction. (Allocating memory about Row Cache new tx) CR ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 BH V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 For processing TX, Address is allocated in v$transaction data at the very first
  • 9. SGA Undo SegmentData Block Shared Pool Buffer Cache 3. Xidusn's value is allocated in v$transaction. (No. 7 usn in here) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 BH V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 After allocating address, USN(Undo Segment Number) is registered in v$transaction data for the second time Undo Segment Number
  • 10. SGA Undo SegmentData Block Shared Pool Buffer Cache Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 4. In Undo segment, Slot value is changed from 9 to 10 Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Block Address 10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2 Undo slot active V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 Undo Segment Number
  • 11. SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 5. Update value A to B of XCU block in Buffer Cache ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 10 0x80 0x04ed 0x0000 0x0000.003dbe4d 0x018000a2 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Undo slot active V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : 0000000069B01FB0 7 BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 CR Update ‘A’ to ‘B’ of CU block CleanOut : Itl No.1 change (--U-  C---) Txn data change: Itl No.2 change (Xid,Uba) Lock Byte change: 0x1  0x2 Undo Segment Number
  • 12. SGA Undo SegmentData Block Shared Pool Buffer Cache V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : 0000000069B01FB0 status : IDLE xidusn : 7 ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 6. Allocate into other column except xid and uba in v$transaction ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 ASCII HEXA code 41 => Value ‘A’ Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 0x018000a2 7 0000000069B01FB0 1 1261 162 ACTIVE Undo Block Address Before image value ‘A’ Undo slot active 6 469 10 0x80 0x04ed 0x0000 0x0000.003dbe4d BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x1 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Registered with the order as below in v$transaction. * addr->xidusn-> xidslot, xidsqn, ubablk
  • 13. SGA Undo SegmentData Block Shared Pool Buffer Cache BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 0x00 9 0x00 0x04ec 0x0001 0x0000.003d6d72 0x00000000 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 10 0x80 0x04ed 0x0000 0x0000.003dbe4d BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 7. Commit execute (Allocating equal scn to Itl slot and undo header slot) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 ASCII HEXA code 41 => Value ‘A’ Undo Block * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a20x0000.003dbe4e --U- 1 fsc 0x0000.003dbe4e Undo slot active Allocating equal scn to Itl slot and undo header slot V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : After commit, TX data is deleted in v$transaction Commit;
  • 14. SGA Undo SegmentData Block Shared Pool Buffer Cache 8. Executing Check point (CU block reflects disk block) ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a2 tl: 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 Value 'B' reflects Data block 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e Undo slot active BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 10 0x80 0x04ed 0x0000 0x0000.003dbe4d0x0000.003dbe4e V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : Check Point;
  • 15. SGA Undo SegmentData Block Shared Pool Buffer Cache ITL Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f88 tl: 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 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e Summary : DML Operation in a Data Block Undo Header index state cflags wrap# uel scn dba parent-xid nub ------------------------------------------------------------------------------------------- 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 * Rec #0x1 slt: 0x00 objn: 70670 (0x0001140e) objd: Undo type: Regular undo Begin trans Last buffer split: No ncol: 2 nnew: 1 size: 0 Vector content: col 1: [ 1] 41 BH (0x643e4b50) file#: 6 rdba: 0x018000a2 (6/162) class: 30 ba: 0x64184000 st: XCURRENT md: EXCL fpin: 'kcbwh2: kcbchg1' tch: 0 Before image value ‘A’ Undo Block Address 0x018000a2 Undo slot active BH (0x643fa438) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643ba000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 --U- 1 fsc 0x0000.003dbe3a 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 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 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 1: [ 1] 42 10 0x80 0x04ed 0x0000 0x0000.003dbe4d0x0000.003dbe4e Value 'B' reflects Data block V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- ------------------------------ addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn :
  • 16. Oracle Deep Internal More information https://youtu.be/s304cY8-IjMYouku Blog Video E-mail NAVER http://cafe.naver.com/playexem ITPUB http://blog.itpub.net/31135309/ Wordpress https://playexem.wordpress.com/ Youtube https://www.youtube.com/channel/ UC5wKR_-A0eL_Pn_EMzoauJg playexem@ex-em.com playexem@naver.com For more information, or to schedule an on-site education, contact via blog or e-mail Kon Woo, Kwon Kun Oh, Lee Sook jin, Kim Dae Deok, Lee