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

Recommendations

Info

CHAPTER 9 ■ REDO AND UNDO 315 blocks we modify exceeds 10 percent of the block buffer cache size, Oracle will stop allocating new lists for us. For example, if our buffer cache is set to cache 3,000 blocks, Oracle will maintain a list of up to 300 blocks (10 percent of 3,000) for us. Upon COMMIT, Oracle will process each of these lists of 20 block pointers, and if the block is still available, it will perform a fast cleanout. So, as long as the number of blocks we modify does not exceed 10 percent of the number of blocks in the cache and our blocks are still in the cache and available to us, Oracle will clean them out upon COMMIT. Otherwise, it just skips them (i.e., does not clean them out). Given this understanding, we can set up artificial conditions to see how the cleanout works. I set my DB_CACHE_SIZE to a low value of 4MB, which is sufficient to hold 512 8KB blocks (my blocksize is 8KB). Then, I created a table such that a row fits on exactly one block—I’ll never have two rows per block. Then, I fill this table up with 500 rows and COMMIT. I’ll measure the amount of redo I have generated so far, run a SELECT that will visit each block, and then measure the amount of redo that SELECT generated. Surprising to many people, the SELECT will have generated redo. Not only that, but it will also have “dirtied” these modified blocks, causing DBWR to write them again. This is due to the block cleanout. Next, I’ll run the SELECT once again and see that no redo is generated. This is expected, as the blocks are all “clean” at this point. ops$tkyte@ORA10G> create table t 2 ( x char(2000), 3 y char(2000), 4 z char(2000) 5 ) 6 / Table created. ops$tkyte@ORA10G> set autotrace traceonly statistics ops$tkyte@ORA10G> insert into t 2 select 'x', 'y', 'z' 3 from all_objects 4 where rownum commit; Commit complete. So, this is my table with one row per block (in my 8KB blocksize database). Now I will measure the amount of redo generated during the read of the data: ops$tkyte@ORA10G> select * 2 from t; 500 rows selected. Statistics ----------------------------------------------------------
316 CHAPTER 9 ■ REDO AND UNDO ... ... 36484 redo size 500 rows processed So, this SELECT generated about 35KB of redo during its processing. This represents the block headers it modified during the full scan of T. DBWR will be writing these modified blocks back out to disk at some point in the future. Now, if I run the query again ops$tkyte@ORA10G> select * 2 from t; 500 rows selected. Statistics ---------------------------------------------------------- ... 0 redo size ... 500 rows processed ops$tkyte@ORA10G> set autotrace off I see that no redo is generated—the blocks are all clean. If we were to rerun the preceding example with the buffer cache set to hold at least 5,000 blocks, we’ll find that we generate little to no redo on any of the SELECTs—we will not have to clean dirty blocks during either of our SELECT statements. This is because the 500 blocks we modified fit comfortably into 10 percent of our buffer cache, and we are the only users. There is no one else mucking around with the data, and no one else is causing our data to be flushed to disk or accessing those blocks. In a live system, it will be normal for at least some of the blocks to not be cleaned out sometimes. This behavior will most affect you after a large INSERT (as just demonstrated), UPDATE, or DELETE—one that affects many blocks in the database (anything more than 10 percent of the size of the cache will definitely do it). You will notice that the first query to touch the block after this will generate a little redo and dirty the block, possibly causing it to be rewritten if DBWR had already flushed it or the instance had been shut down, clearing out the buffer cache altogether. There is not too much you can do about it. It is normal and to be expected. If Oracle did not do this deferred cleanout of a block, a COMMIT could take as long to process as the transaction itself. The COMMIT would have to revisit each and every block, possibly reading them in from disk again (they could have been flushed). If you are not aware of block cleanouts and how they work, it will be one of those mysterious things that just seems to happen for no reason. For example, say you UPDATE a lot of data and COMMIT. Now you run a query against that data to verify the results. The query appears to generate tons of write I/O and redo. It seems impossible if you are unaware of block cleanouts; it was to me the first time I saw it. You go and get someone to observe this behavior with you, but it is not reproducible, as the blocks are now “clean” on the second query. You simply write it off as one of those database mysteries.
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:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Page 260 and 261:
Page 262 and 263:
Page 264 and 265:
Page 266 and 267:
Page 268 and 269:
Page 270 and 271:
Page 272 and 273:
Page 274 and 275:
Page 276 and 277:
CHAPTER 7 ■ ■ ■ Concurrency a
Page 278 and 279:
CHAPTER 7 ■ CONCURRENCY AND MULTI
Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
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 359: 314 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 371 and 372: 326 CHAPTER 9 ■ REDO AND UNDO wil
Page 373 and 374: 328 CHAPTER 9 ■ REDO AND UNDO Thi
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 411 and 412:
366 CHAPTER 10 ■ DATABASE TABLES
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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?