Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

Recommendations

Info

CHAPTER 7 ■ CONCURRENCY AND MULTI-VERSIONING 249 Table 7-8. Sequence of Updates Time Session 1 Session 2 Comment T1 Update t This updates the one row that matches the set y = 10 criteria. where y = 5; T2 Update t Using consistent reads, this will find the Set x = x+1 record session 1 modified, but it won’t be Where y = 5; able to update it since session 1 has it blocked. Session 2 will block and wait for this row. T3 Commit; This releases session 1; session 1 becomes unblocked. It can finally do the current read on the block containing this row, where Y was equal to 5 when session 1 began its update. So the record that was Y=5 when you began the UPDATE is no longer Y=5. The consistent read component of the UPDATE says, “You want to update this record because Y was 5 when we began,” but the current version of the block makes you think, “Oh, no, I cannot update this row because Y isn’t 5 anymore—it would be wrong.” If we just skipped this record at this point and ignored it, then we would have a nondeterministic update. It would be throwing data consistency and integrity out the window. The outcome of the update (how many and which rows were modified) would depend on the order in which rows got hit in the table and what other activity just happened to be going on. You could take the same exact set of rows and in two different databases, each one running the transactions in exactly the same mix, you could observe different results, just because the rows were in different places on the disk. In this case, Oracle chose to restart the update. When the row that was Y=5 when you started is found to contain the value Y=10, Oracle will silently roll back your update and restart it—assuming you are using READ COMMITTED isolation. If you are using SERIALIZABLE isolation, then at this point you would receive an ORA-08177: can't serialize access error for this transaction. In READ COMMITTED mode, after the transaction rolls back your update, the database will restart the update (i.e., change the point in time at which the update is “as of”), and instead of updating the data again, it will go into SELECT FOR UPDATE mode and attempt to lock all of the rows WHERE Y=5 for your session. Once it does this, it will run the UPDATE against that locked set of data, thus ensuring this time that it can complete without restarting. But to continue on with the “but what happens . . .” train of thought, what happens if after restarting the update and going into SELECT FOR UPDATE mode (which has the same readconsistent and read current block gets going on as an update does), a row that was Y=5 when you started the SELECT FOR UPDATE is found to be Y=11 when you go to get the current version of it? That SELECT FOR UDPDATE will restart and the cycle begins again. There are two questions to be addressed here—two questions that interested me, anyway. The first is, Can we observe this? Can we see this actually happen? And the second is, So what? What does this actually mean to us as developers? We’ll address these questions in turn now. Seeing a Restart It is easier to see a restart than you might at first think. We’ll be able to observe one, in fact, using a simple one-row table. This is the table we’ll use to test with:
250 CHAPTER 7 ■ CONCURRENCY AND MULTI-VERSIONING ops$tkyte@ORA10G> create table t ( x int, y int ); Table created. ops$tkyte@ORA10G> insert into t values ( 1, 1 ); 1 row created. ops$tkyte@ORA10G> commit; Commit complete. To observe the restart, all we need is a trigger to print out some information. We’ll use a BEFORE UPDATE FOR EACH ROW trigger to simply print out the before and after image of the row as the result of an update: ops$tkyte@ORA10G> create or replace trigger t_bufer 2 before update on t for each row 3 begin 4 dbms_output.put_line 5 ( 'old.x = ' || :old.x || 6 ', old.y = ' || :old.y ); 7 dbms_output.put_line 8 ( 'new.x = ' || :new.x || 9 ', new.y = ' || :new.y ); 10 end; 11 / Trigger created. Now we’ll update that row: ops$tkyte@ORA10G> set serveroutput on ops$tkyte@ORA10G> update t set x = x+1; old.x = 1, old.y = 1 new.x = 2, new.y = 1 1 row updated. So far, everything is as we expect: the trigger fired once, and we see the old and new values. Note that we have not yet committed, however—the row is still locked. In another session, we’ll execute this update: ops$tkyte@ORA10G> set serveroutput on ops$tkyte@ORA10G> update t set x = x+1 where x > 0; That will immediately block, of course, since the first session has that row locked. If we now go back to the first session and commit, we’ll see this output (the update is repeated for clarity) in the second session: ops$tkyte@ORA10G> update t set x = x+1 where x > 0; old.x = 1, old.y = 1 new.x = 2, new.y = 1 old.x = 2, old.y = 1 new.x = 3, new.y = 1
Page 2 and 3:
Expert Oracle Database Architecture
Page 4 and 5:
Contents Foreword . . . . . . . . .
Page 6 and 7:
■CONTENTS v Block Buffer Cache .
Page 8 and 9:
■CONTENTS vii ■CHAPTER 9 Redo a
Page 10 and 11:
■CONTENTS ix ■CHAPTER 12 Dataty
Page 12 and 13:
Foreword “THINK.” In 1914, Thom
Page 14 and 15:
■FOREWORD xiii Tom is an aficiona
Page 16 and 17:
About the Technical Reviewers ■JO
Page 18 and 19:
Introduction The inspiration for th
Page 20 and 21:
■INTRODUCTION xix • Exposure to
Page 22 and 23:
■INTRODUCTION xxi Chapter 3: File
Page 24 and 25:
■INTRODUCTION xxiii Next up are t
Page 26 and 27:
Setting Up Your Environment In this
Page 28 and 29:
■SETTING UP YOUR ENVIRONMENT xxvi
Page 30 and 31:
■SETTING UP YOUR ENVIRONMENT xxix
Page 32 and 33:
■SETTING UP YOUR ENVIRONMENT xxxi
Page 34 and 35:
Page 36 and 37:
■SETTING UP YOUR ENVIRONMENT xxxv
Page 38 and 39:
■SETTING UP YOUR ENVIRONMENT xxxv
Page 40 and 41:
Page 42 and 43:
■SETTING UP YOUR ENVIRONMENT xli
Page 44 and 45:
■SETTING UP YOUR ENVIRONMENT xlii
Page 46 and 47:
CHAPTER 1 ■ ■ ■ Developing Su
Page 48 and 49:
CHAPTER 1 ■ DEVELOPING SUCCESSFUL
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92:
Page 95 and 96:
50 CHAPTER 2 ■ ARCHITECTURE OVERV
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 110 and 111:
CHAPTER 3 ■ ■ ■ Files In this
Page 112 and 113:
CHAPTER 3 ■ FILES 67 Without a pa
Page 114 and 115:
CHAPTER 3 ■ FILES 69 and even dat
Page 116 and 117:
CHAPTER 3 ■ FILES 71 all operatio
Page 118 and 119:
CHAPTER 3 ■ FILES 73 *.cluster_da
Page 120 and 121:
CHAPTER 3 ■ FILES 75 ops$tkyte@OR
Page 122 and 123:
CHAPTER 3 ■ FILES 77 • To maint
Page 124 and 125:
CHAPTER 3 ■ FILES 79 • Resource
Page 126 and 127:
CHAPTER 3 ■ FILES 81 3 l_dummy nu
Page 128 and 129:
CHAPTER 3 ■ FILES 83 Trace Files
Page 130 and 131:
CHAPTER 3 ■ FILES 85 _qerixAlloca
Page 132 and 133:
CHAPTER 3 ■ FILES 87 6 ( 7 TYPE O
Page 134 and 135:
CHAPTER 3 ■ FILES 89 A Brief Revi
Page 136 and 137:
CHAPTER 3 ■ FILES 91 Redundant Ar
Page 138 and 139:
CHAPTER 3 ■ FILES 93 (data from m
Page 140 and 141:
CHAPTER 3 ■ FILES 95 dictionary t
Page 142 and 143:
CHAPTER 3 ■ FILES 97 ■Note df i
Page 144 and 145:
CHAPTER 3 ■ FILES 99 “accidenta
Page 146 and 147:
CHAPTER 3 ■ FILES 101 So, at the
Page 148 and 149:
CHAPTER 3 ■ FILES 103 Password Fi
Page 150 and 151:
CHAPTER 3 ■ FILES 105 USER is "SY
Page 152 and 153:
CHAPTER 3 ■ FILES 107 Flashback L
Page 154 and 155:
CHAPTER 3 ■ FILES 109 of the requ
Page 156 and 157:
CHAPTER 3 ■ FILES 111 IMPDP, howe
Page 158 and 159:
CHAPTER 3 ■ FILES 113 tkyte@ORA10
Page 160 and 161:
CHAPTER 4 ■ ■ ■ Memory Struct
Page 162 and 163:
CHAPTER 4 ■ MEMORY STRUCTURES 117
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
CHAPTER 5 ■ ■ ■ Oracle Proces
Page 202 and 203:
CHAPTER 5 ■ ORACLE PROCESSES 157
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
CHAPTER 6 ■ ■ ■ Locking and L
Page 230 and 231:
CHAPTER 6 ■ LOCKING AND LATCHING
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245: CHAPTER 6 ■ LOCKING AND LATCHING
Page 276 and 277: CHAPTER 7 ■ ■ ■ Concurrency a
Page 278 and 279: CHAPTER 7 ■ CONCURRENCY AND MULTI
Page 300 and 301: CHAPTER 8 ■ ■ ■ Transactions
Page 302 and 303: CHAPTER 8 ■ TRANSACTIONS 257 •
Page 304 and 305: CHAPTER 8 ■ TRANSACTIONS 259 So,
Page 306 and 307: CHAPTER 8 ■ TRANSACTIONS 261 X --
Page 308 and 309: CHAPTER 8 ■ TRANSACTIONS 263 “s
Page 310 and 311: CHAPTER 8 ■ TRANSACTIONS 265 busi
Page 312 and 313: CHAPTER 8 ■ TRANSACTIONS 267 Many
Page 314 and 315: CHAPTER 8 ■ TRANSACTIONS 269 ops$
Page 316 and 317: CHAPTER 8 ■ TRANSACTIONS 271 last
Page 318 and 319: CHAPTER 8 ■ TRANSACTIONS 273 Dist
Page 320 and 321: CHAPTER 8 ■ TRANSACTIONS 275 Auto
Page 322 and 323: CHAPTER 8 ■ TRANSACTIONS 277 3 Au
Page 324 and 325: CHAPTER 8 ■ TRANSACTIONS 279 5 pr
Page 326: CHAPTER 8 ■ TRANSACTIONS 281 scot
Page 329 and 330: 284 CHAPTER 9 ■ REDO AND UNDO cri
Page 331 and 332: 286 CHAPTER 9 ■ REDO AND UNDO Fir
Page 333 and 334: 288 CHAPTER 9 ■ REDO AND UNDO The
Page 335 and 336: 290 CHAPTER 9 ■ REDO AND UNDO We
Page 337 and 338: 292 CHAPTER 9 ■ REDO AND UNDO Wha
Page 339 and 340: 294 CHAPTER 9 ■ REDO AND UNDO row
Page 341 and 342: 296 CHAPTER 9 ■ REDO AND UNDO If
Page 343 and 344: 298 CHAPTER 9 ■ REDO AND UNDO ops
Page 345 and 346:
300 CHAPTER 9 ■ REDO AND UNDO Inv
Page 347 and 348:
302 CHAPTER 9 ■ REDO AND UNDO The
Page 349 and 350:
304 CHAPTER 9 ■ REDO AND UNDO 41
Page 351 and 352:
306 CHAPTER 9 ■ REDO AND UNDO ins
Page 353 and 354:
308 CHAPTER 9 ■ REDO AND UNDO So,
Page 355 and 356:
310 CHAPTER 9 ■ REDO AND UNDO ops
Page 357 and 358:
Page 359 and 360:
314 CHAPTER 9 ■ REDO AND UNDO •
Page 361 and 362:
316 CHAPTER 9 ■ REDO AND UNDO ...
Page 363 and 364:
318 CHAPTER 9 ■ REDO AND UNDO •
Page 365 and 366:
320 CHAPTER 9 ■ REDO AND UNDO bac
Page 367 and 368:
322 CHAPTER 9 ■ REDO AND UNDO As
Page 369 and 370:
Page 371 and 372:
326 CHAPTER 9 ■ REDO AND UNDO wil
Page 373 and 374:
328 CHAPTER 9 ■ REDO AND UNDO Thi
Page 375 and 376:
Page 377 and 378:
332 CHAPTER 9 ■ REDO AND UNDO Whe
Page 379 and 380:
334 CHAPTER 9 ■ REDO AND UNDO Tha
Page 381 and 382:
336 CHAPTER 9 ■ REDO AND UNDO tou
Page 383 and 384:
338 CHAPTER 10 ■ DATABASE TABLES
Page 385 and 386:
Page 387 and 388:
Page 389 and 390:
Page 391 and 392:
Page 393 and 394:
Page 395 and 396:
Page 397 and 398:
Page 399 and 400:
Page 401 and 402:
Page 403 and 404:
Page 405 and 406:
Page 407 and 408:
Page 409 and 410:
Page 411 and 412:
Page 413 and 414:
Page 415 and 416:
Page 417 and 418:
Page 419 and 420:
Page 421 and 422:
Page 423 and 424:
Page 425 and 426:
Page 427 and 428:
Page 429 and 430:
Page 431 and 432:
Page 433 and 434:
Page 435 and 436:
Page 437 and 438:
Page 439 and 440:
Page 441 and 442:
Page 443 and 444:
Page 445 and 446:
Page 447 and 448:
Page 449 and 450:
Page 451 and 452:
Page 453 and 454:
Page 455 and 456:
Page 457 and 458:
Page 459 and 460:
Page 461 and 462:
Page 463 and 464:
Page 466 and 467:
CHAPTER 11 ■ ■ ■ Indexes Inde
Page 468 and 469:
CHAPTER 11 ■ INDEXES 423 value of
Page 470 and 471:
CHAPTER 11 ■ INDEXES 425 One of t
Page 472 and 473:
CHAPTER 11 ■ INDEXES 427 We then
Page 474 and 475:
CHAPTER 11 ■ INDEXES 429 we ended
Page 476 and 477:
CHAPTER 11 ■ INDEXES 431 The data
Page 478 and 479:
CHAPTER 11 ■ INDEXES 433 if ( (++
Page 480 and 481:
CHAPTER 11 ■ INDEXES 435 Table 11
Page 482 and 483:
CHAPTER 11 ■ INDEXES 437 When Sho
Page 484 and 485:
CHAPTER 11 ■ INDEXES 439 an 8KB b
Page 486 and 487:
CHAPTER 11 ■ INDEXES 441 select *
Page 488 and 489:
Page 490 and 491:
CHAPTER 11 ■ INDEXES 445 Indicate
Page 492 and 493:
CHAPTER 11 ■ INDEXES 447 an index
Page 494 and 495:
CHAPTER 11 ■ INDEXES 449 Table 11
Page 496 and 497:
CHAPTER 11 ■ INDEXES 451 9 1, 'M'
Page 498 and 499:
CHAPTER 11 ■ INDEXES 453 column w
Page 500 and 501:
CHAPTER 11 ■ INDEXES 455 Bitmap j
Page 502 and 503:
CHAPTER 11 ■ INDEXES 457 INSERT a
Page 504 and 505:
CHAPTER 11 ■ INDEXES 459 7 l_last
Page 506 and 507:
CHAPTER 11 ■ INDEXES 461 ops$tkyt
Page 508 and 509:
CHAPTER 11 ■ INDEXES 463 If we co
Page 510 and 511:
Page 512 and 513:
CHAPTER 11 ■ INDEXES 467 Caveat o
Page 514 and 515:
Page 516 and 517:
CHAPTER 11 ■ INDEXES 471 Frequent
Page 518 and 519:
Page 520 and 521:
CHAPTER 11 ■ INDEXES 475 If you s
Page 522 and 523:
CHAPTER 11 ■ INDEXES 477 we’ll
Page 524 and 525:
CHAPTER 11 ■ INDEXES 479 Predicat
Page 526 and 527:
Page 528 and 529:
Page 530 and 531:
CHAPTER 11 ■ INDEXES 485 This dem
Page 532 and 533:
CHAPTER 11 ■ INDEXES 487 SELECT /
Page 534 and 535:
CHAPTER 12 ■ ■ ■ Datatypes Ch
Page 536 and 537:
CHAPTER 12 ■ DATATYPES 491 • TI
Page 538 and 539:
CHAPTER 12 ■ DATATYPES 493 (in th
Page 540 and 541:
CHAPTER 12 ■ DATATYPES 495 That d
Page 542 and 543:
CHAPTER 12 ■ DATATYPES 497 ops$tk
Page 544 and 545:
CHAPTER 12 ■ DATATYPES 499 Table
Page 546 and 547:
CHAPTER 12 ■ DATATYPES 501 The IN
Page 548 and 549:
Page 550 and 551:
CHAPTER 12 ■ DATATYPES 505 • BI
Page 552 and 553:
CHAPTER 12 ■ DATATYPES 507 NUMBER
Page 554 and 555:
CHAPTER 12 ■ DATATYPES 509 MSG NU
Page 556 and 557:
CHAPTER 12 ■ DATATYPES 511 They a
Page 558 and 559:
CHAPTER 12 ■ DATATYPES 513 ■Not
Page 560 and 561:
CHAPTER 12 ■ DATATYPES 515 Coping
Page 562 and 563:
CHAPTER 12 ■ DATATYPES 517 Note t
Page 564 and 565:
CHAPTER 12 ■ DATATYPES 519 We are
Page 566 and 567:
CHAPTER 12 ■ DATATYPES 521 Format
Page 568 and 569:
Page 570 and 571:
CHAPTER 12 ■ DATATYPES 525 You ca
Page 572 and 573:
CHAPTER 12 ■ DATATYPES 527 month
Page 574 and 575:
CHAPTER 12 ■ DATATYPES 529 DT2-DT
Page 576 and 577:
CHAPTER 12 ■ DATATYPES 531 DT TS
Page 578 and 579:
Page 580 and 581:
CHAPTER 12 ■ DATATYPES 535 Since
Page 582 and 583:
Page 584 and 585:
Page 586 and 587:
CHAPTER 12 ■ DATATYPES 541 suppor
Page 588 and 589:
CHAPTER 12 ■ DATATYPES 543 Concep
Page 590 and 591:
CHAPTER 12 ■ DATATYPES 545 We can
Page 592 and 593:
CHAPTER 12 ■ DATATYPES 547 buffer
Page 594 and 595:
CHAPTER 12 ■ DATATYPES 549 Note t
Page 596 and 597:
CHAPTER 12 ■ DATATYPES 551 13 dbm
Page 598 and 599:
CHAPTER 12 ■ DATATYPES 553 equall
Page 600 and 601:
CHAPTER 12 ■ DATATYPES 555 ROWID/
Page 602 and 603:
CHAPTER 13 ■ ■ ■ Partitioning
Page 604 and 605:
CHAPTER 13 ■ PARTITIONING 559 6 (
Page 606 and 607:
CHAPTER 13 ■ PARTITIONING 561 els
Page 608 and 609:
CHAPTER 13 ■ PARTITIONING 563 BIG
Page 610 and 611:
CHAPTER 13 ■ PARTITIONING 565 Enh
Page 612 and 613:
CHAPTER 13 ■ PARTITIONING 567 Tab
Page 614 and 615:
CHAPTER 13 ■ PARTITIONING 569 tha
Page 616 and 617:
CHAPTER 13 ■ PARTITIONING 571 PAR
Page 618 and 619:
CHAPTER 13 ■ PARTITIONING 573 35
Page 620 and 621:
CHAPTER 13 ■ PARTITIONING 575 If
Page 622 and 623:
CHAPTER 13 ■ PARTITIONING 577 We
Page 624 and 625:
Page 626 and 627:
CHAPTER 13 ■ PARTITIONING 581 ops
Page 628 and 629:
CHAPTER 13 ■ PARTITIONING 583 In
Page 630 and 631:
Page 632 and 633:
CHAPTER 13 ■ PARTITIONING 587 | S
Page 634 and 635:
Page 636 and 637:
Page 638 and 639:
CHAPTER 13 ■ PARTITIONING 593 •
Page 640 and 641:
CHAPTER 13 ■ PARTITIONING 595 Now
Page 642 and 643:
CHAPTER 13 ■ PARTITIONING 597 the
Page 644 and 645:
CHAPTER 13 ■ PARTITIONING 599 imp
Page 646 and 647:
CHAPTER 13 ■ PARTITIONING 601 OLT
Page 648 and 649:
CHAPTER 13 ■ PARTITIONING 603 5 s
Page 650 and 651:
CHAPTER 13 ■ PARTITIONING 605 Sur
Page 652 and 653:
CHAPTER 13 ■ PARTITIONING 607 On
Page 654 and 655:
CHAPTER 13 ■ PARTITIONING 609 Row
Page 656 and 657:
CHAPTER 13 ■ PARTITIONING 611 So,
Page 658 and 659:
CHAPTER 13 ■ PARTITIONING 613 Aud
Page 660 and 661:
CHAPTER 14 ■ ■ ■ Parallel Exe
Page 662 and 663:
CHAPTER 14 ■ PARALLEL EXECUTION 6
Page 664 and 665:
Page 666 and 667:
Page 668 and 669:
Page 670 and 671:
Page 672 and 673:
Page 674 and 675:
Page 676 and 677:
Page 678 and 679:
Page 680 and 681:
Page 682 and 683:
Page 684 and 685:
Page 686 and 687:
Page 688 and 689:
Page 690 and 691:
Page 692 and 693:
Page 694 and 695:
CHAPTER 15 ■ ■ ■ Data Loading
Page 696 and 697:
CHAPTER 15 ■ DATA LOADING AND UNL
Page 698 and 699:
Page 700 and 701:
Page 702 and 703:
Page 704 and 705:
Page 706 and 707:
Page 708 and 709:
Page 710 and 711:
Page 712 and 713:
Page 714 and 715:
Page 716 and 717:
Page 718 and 719:
Page 720 and 721:
Page 722 and 723:
Page 724 and 725:
Page 726 and 727:
Page 728 and 729:
Page 730 and 731:
Page 732 and 733:
Page 734 and 735:
Page 736 and 737:
Page 738 and 739:
Page 740 and 741:
Page 742 and 743:
Page 744 and 745:
Page 746 and 747:
Page 748:
Page 751 and 752:
706 ■INDEX autonomous transaction
Page 753 and 754:
708 ■INDEX CREATE ANY DIRECTORY f
Page 755 and 756:
710 ■INDEX dedicated server, 57-5
Page 757 and 758:
712 ■INDEX flat files, 66, 113-14
Page 759 and 760:
714 ■INDEX job queue coordinator
Page 761 and 762:
716 ■INDEX MAXTRANS parameter, 21
Page 763 and 764:
718 ■INDEX parameter files (PFILE
Page 765 and 766:
720 ■INDEX REUSE option, 97 REUSE
Page 767 and 768:
722 ■INDEX System Global Area (SG
Page 769:
724 ■INDEX utility background pro
show all

Apress.Expert.Oracle.Database.Architecture.9i.and.10g.Programming.Techniques.and.Solutions.Sep.2005

Create successful ePaper yourself

Delete template?

Save as template?