Oracle Deep Internal 2 (ver.2)
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The document describes the Oracle undo segment and how it tracks changes to data in transactions. 1) It shows the initial state when a value of "A" is entered into a table column. 2) It then shows an update transaction that changes the value from "A" to "B", with the undo segment recording the before image of "A". 3) A second update transaction is shown, changing the value from "B" to "C", with the undo segment recording the before images of "B" and "A".
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Oracle Deep Internal 2 (ver.2)
- 1. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ver.2 (2016.07.19)
- 2. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Cited from http://wiki.gurubee.net/display/STUDY/1st_Undo "Undo record chain" mechanism as explained in Gurubee site It's so difficult to understand only through the book. I'd like to check internal actual situation of oracle with my own eyes
- 3. SGA Undo Segment Shared Pool Buffer Cache © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Data Block Undo Header index 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 * Rec #0x1 BH ITL Itl Xid Uba Flag Lck Scn/Fsc 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 0. Initial state when a value of "A" is entered (The first stage before update) V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- -------------------- addr : status : IDLE xidusn : ubafil : start_date : 2015-12-10 10:52:46 xidslot : ubablk : ses_addr : 000000006B21CC20 xidsqn : ubasqn : ASCII HEXA code 41 => Value ‘A’
- 4. SGA Undo Segment Shared Pool Buffer Cache © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- -------------------------------- addr : 0000000069B24E78 ubafil : 6 status : ACTIVE xidusn : 10 ubablk : 210 start_date : 2016-01-13 18:57:04 xidslot : 0 ubasqn : 532 ses_addr : 000000006B21CC20 xidsqn : 1424 ubarec : 1 1. UPDATE T1 SET C2='B' Undo Header index state cflags wrap# uel scn dba ------------------------------------------------------------------------------------------ 0x00 10 0x80 0x0590 0x0000 0x0000.004c2039 0x018000d2 0x01 9 0x00 0x058f 0x0002 0x0000.004bca7f 0x00000000 Undo Block BH (0x643fb068) file#: 6 rdba: 0x018000d2 (6/210) class: 36 ba: 0x643ce000 xid: 0x000a.000.00000590 seq: 0x214 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 Rec Offset Rec Offset Rec Offset Rec Offset Rec Offset --------------------------------------------------------------------------- 0x01 0x1f44 *----------------------------- * Rec #0x1 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x00 op: Z itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 41 BH (0x643fb1a0) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d0000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.01 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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 BH (0x643fb2d8) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d2000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Uba+seq+record# After Image ASCII HEXA code 42 => Value ‘B’ Before Image ASCII HEXA code 41 => Value ‘A’ Before Image ASCII HEXA code 41 => Value ‘A’ UPDATE T1 SET c2 = ‘B’
- 5. SGA Undo Segment Shared Pool Buffer Cache © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 2. UPDATE T1 SET C2=‘C' BH (0x643f8e48) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x64396000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.02 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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] 43 BH (0x643fb2d8) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d2000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 BH (0x643fb1a0) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d0000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.01 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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 V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- -------------------------------- addr : 0000000069B24E78 ubafil : 6 status : ACTIVE xidusn : 10 ubablk : 210 start_date : 2016-01-13 18:57:04 xidslot : 0 ubasqn : 532 ses_addr : 000000006B21CC20 xidsqn : 1424 ubarec : 2 After Image ASCII HEXA code 43 => Value ‘C’ After Image ASCII HEXA code 42 => Value ‘B’ Undo Header index state cflags wrap# uel scn dba ------------------------------------------------------------------------------------------ 0x00 10 0x80 0x0590 0x0000 0x0000.004c2039 0x018000d2 0x01 9 0x00 0x058f 0x0002 0x0000.004bca7f 0x00000000 Undo Block BH (0x643fb068) file#: 6 rdba: 0x018000d2 (6/210) class: 36 ba: 0x643ce000 xid: 0x000a.000.00000590 seq: 0x214 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 Rec Offset Rec Offset Rec Offset Rec Offset Rec Offset --------------------------------------------------------------------------- 0x01 0x1f44 *----------------------------- * Rec #0x1 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x00 op: Z itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 41 *----------------------------- * Rec #0x2 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x01 op: C uba: 0x018000d2.0214.01 itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 42 Before Image ASCII HEXA code 41 => Value ‘A’ Before Image ASCII HEXA code 42 => Value ‘B’ UPDATE T1 SET c2 = ‘C’
- 6. SGA Undo Segment Shared Pool Buffer Cache © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 3. UPDATE T1 SET C2=‘D' BH (0x643f8968) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x6438e000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.03 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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] 44 BH (0x643fb2d8) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d2000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 BH (0x643fb1a0) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d0000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.01 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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 BH (0x643f8e48) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x64396000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.02 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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] 43 V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- -------------------------------- addr : 0000000069B24E78 ubafil : 6 status : ACTIVE xidusn : 10 ubablk : 210 start_date : 2016-01-13 18:57:04 xidslot : 0 ubasqn : 532 ses_addr : 000000006B21CC20 xidsqn : 1424 ubarec : 3 After Image ASCII HEXA code 44 => Value ‘D’ After Image ASCII HEXA code 43 => Value ‘C’ Undo Header index state cflags wrap# uel scn dba ------------------------------------------------------------------------------------------ 0x00 10 0x80 0x0590 0x0000 0x0000.004c2039 0x018000d2 0x01 9 0x00 0x058f 0x0002 0x0000.004bca7f 0x00000000 Undo Block BH (0x643fb068) file#: 6 rdba: 0x018000d2 (6/210) class: 36 ba: 0x643ce000 xid: 0x000a.000.00000590 seq: 0x214 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 Rec Offset Rec Offset Rec Offset Rec Offset Rec Offset --------------------------------------------------------------------------- 0x01 0x1f44 * Rec #0x1 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x00 op: Z itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 41 * Rec #0x2 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x01 op: C uba: 0x018000d2.0214.01 itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 42 * Rec #0x3 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x02 op: C uba: 0x018000d2.0214.02 itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 43 Before Image ASCII HEXA code 43 => Value ‘C’ UPDATE T1 SET c2 = ‘D’
- 7. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 4. Summary
- 8. SGA Undo Segment Shared Pool Buffer Cache © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Data Block 4. Summary BH (0x643f8968) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x6438e000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.03 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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] 44 BH (0x643fb2d8) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d2000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 BH (0x643fb1a0) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x643d0000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.01 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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 BH (0x643f8e48) file#: 5 rdba: 0x0140dcab (5/56491) class: 1 ba: 0x64396000 st: CR md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x0006.000.0000056a 0x00000000.0000.00 C--- 0 scn 0x0000.004c2027 0x02 0x000a.000.00000590 0x018000d2.0214.02 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 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] 43 V$transaction XID_INFO UBA_INFO TXN_INFO -------------------------- --------------- -------------------------------- addr : 0000000069B24E78 ubafil : 6 status : ACTIVE xidusn : 10 ubablk : 210 start_date : 2016-01-13 18:57:04 xidslot : 0 ubasqn : 532 ses_addr : 000000006B21CC20 xidsqn : 1424 ubarec : 3 After Image ASCII HEXA code 44 => Value ‘D’ After Image ASCII HEXA code 43 => Value ‘C’ Undo Header index state cflags wrap# uel scn dba ------------------------------------------------------------------------------------------ 0x00 10 0x80 0x0590 0x0000 0x0000.004c2039 0x018000d2 0x01 9 0x00 0x058f 0x0002 0x0000.004bca7f 0x00000000 Undo Block BH (0x643fb068) file#: 6 rdba: 0x018000d2 (6/210) class: 36 ba: 0x643ce000 xid: 0x000a.000.00000590 seq: 0x214 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 Rec Offset Rec Offset Rec Offset Rec Offset Rec Offset --------------------------------------------------------------------------- 0x01 0x1f44 * Rec #0x1 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x00 op: Z itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 41 * Rec #0x2 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x01 op: C uba: 0x018000d2.0214.01 itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 42 * Rec #0x3 slt: 0x00 objn: 70870(0x000114d6) objd: 70870 tblspc: 5(0x00000005) * Layer: 11 (Row) opc: 1 rci 0x02 op: C uba: 0x018000d2.0214.02 itli: 2 ispac: 0 maxfr: 4858 vect = 11 col 1: [ 1] 43 After Image ASCII HEXA code 43 => Value ‘C’ op: C uba: 0x018000d2.0214.02 op: C uba: 0x018000d2.0214.01 op: Z Rec #0x1 Rec #0x2 Rec #0x3
- 9. Oracle Deep Internal Blog Video E-mail NAVER http://cafe.naver.com/playexem ITPUB http://blog.itpub.net/31135309/ Wordpress https://playexem.wordpress.com/ Slideshare http://www.slideshare.net/playexem Youtube https://www.youtube.com/channel/UC 5wKR_-A0eL_Pn_EMzoauJg Research & Contents Team Sook jin, Kim edu@ex-em.com For more information, or to schedule an on-site education, contact via blog or e-mail