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2-48 IBM Informix OnLine Database Server Administrator’s Guide
Shared-Memory Internal Tables
The header also contains the OnLine “magic number,” which is used to
synchronizeuserprocesses.EachOnLinereleaseisassignedamagicnumber.
In addition, the same magic number is contained within the user process
code. Whenever a user process attempts to attach to shared memory, these
magicnumbersarecompared.Iftheyarenotcompatible,anerrorisreturned.
The magic-number check ensures that the database server processes are
compatible.
Shared-Memory Internal Tables
OnLine shared memory contains nine internal tables that track shared-
memory resources. (Refer to Figure 2-5 on page 2-40.) Three of these nine
tables are paired with hash tables. Each of the nine is described next.
OnLine Buffer Table
Thebufferheadertabletrackstheaddressandstatusoftheindividualbuffers
in the shared-memory pool. When a buffer is used, it contains an image of a
data or index page from disk.
The buffer header table contains the following control information, which is
needed for buffer management:
■ Buffer status
Buffer status is described as empty, unmodified, or modified. An
unmodified buffer contains data,but this datacan be overwritten. A
modified, or dirty, buffer contains data that must be written to disk
before it can be overwritten.
■ User processes currently accessing the buffer
Thelistofuserprocessesis storedasabitmap.Eachusersharingthe
buffer accounts for one of the bits set in the bit map and increments
the buffer’s shared-user count, which is stored separately.
■ Current lock-access level
Buffersreceivelock-accesslevelsdependingonthetypeofoperation
the user process is executing. OnLine supports three buffer lock-
access levels: shared, promotable (update), and exclusive.
- IBM Informix OnLine 1
- Database Server 1
- Table of Contents 3
- Chapter 2 System Architecture 5
- Chapter 3 Operating OnLine 7
- Chapter 6 DB-Monitor Screens 12
- Chapter 7 Utilities 12
- Chapter 8 OnLine Message Log 14
- Chapter 9 Product Environment 14
- Appendix A Notices 14
- Introduction 15
- In This Introduction 17
- About This Manual 17
- Organization of This Manual 18
- Demonstration Database 19
- Documentation Conventions 22
- Icon Conventions 23
- Command-Line Conventions 23
- Sample Code Conventions 26
- Additional Documentation 28
- Error Message Files 29
- Related Reading 33
- IBM Welcomes Your Comments 34
- Installation and Initial 35
- Configuration 35
- Define Your Starting Point 40
- Create a Level-0 Archive 42
- Initialize Shared Memory 42
- Create a New Level-0 Archive 43
- OnLine Configuration Files 45
- Contents of tbconfig.std 47
- # System Page Size 54
- ROOTNAME 55
- ROOTPATH 56
- ROOTOFFSET 56
- ROOTSIZE 57
- MIRRORPATH 58
- MIRROROFFSET 59
- PHYSFILE 59
- PHYSDBS is 1,000 KB 60
- LOGFILES 61
- Message File Guidelines 62
- TAPESIZE 63
- LTAPEDEV 64
- LTAPEBLK 64
- LTAPESIZE 65
- DBSERVERNAME 66
- RESIDENT 66
- TRANSACTIONS 67
- TBLSPACES 68
- DBSPACES 69
- PHYSBUFF 69
- CLEANERS 70
- CKPTINTVL 71
- DYNSHMSZ 73
- GTRID_CMP_SZ 73
- DEADLOCK_TIMEOUT 73
- TXTIMEOUT 73
- OnLine Disk Space Allocation 74
- How to Allocate Disk Space 81
- Configuration Checklist 84
- Set configuration parameters 85
- ESC to record the 86
- Initialize OnLine 88
- TBCONFIG 89
- Shutdown 92
- Errors During Initialization 93
- OnLine Error Message Format 94
- UNIX Error Message Format 94
- System Architecture 95
- System Architecture 2-3 97
- System Architecture 2-5 99
- In This Chapter 101
- Initialization 101
- Initialization Commands 102
- Shared Memory Commands 103
- Disk Space Commands 104
- Step 2: Create Shared Memory 106
- Step 5: Wake Parent Process 107
- ■ tbinit -i 108
- ■ tbinit -i -s 108
- Step 5: Initialize Disk Space 110
- System Architecture 2-17 111
- Step 9: Set Forced Residency 112
- SHMBASE 114
- UNIX system might set a 114
- OnLine User Processes 116
- Step 1: Obtain SERVERNUM 118
- (SERVERNUM * 65536) + shmkey 119
- OnLine Daemon Processes 127
- System Architecture 2-35 129
- LRU queue 129
- Buffer Share Lock 132
- Buffer Update Lock 132
- Buffer Exclusive Lock 133
- ■ Buffer locks 134
- ■ Latches 134
- ■ Timestamps 134
- ■ Hash tables 134
- Shared-Memory Latches 135
- Test-and-Set Institutions 136
- Spin and Test Again 136
- Semaphores 137
- Forced Abort 137
- OnLine Timestamps 138
- System Architecture 2-45 139
- Shared-Memory Header 141
- Shared-Memory Internal Tables 142
- OnLine Chunk Table 143
- OnLine Dbspace Table 144
- OnLine Latch Table 145
- OnLine Lock Table 145
- OnLine Page-Cleaner Table 146
- OnLine Tblspace Table 146
- OnLine Transaction Table 148
- OnLine User Table 148
- Shared-Memory Buffer Pool 149
- Regular Buffers 150
- Big Buffers 150
- OnLine LRU Queues 151
- LRU_MAX_DIRTY 153
- LRU_MIN_DIRTY 153
- Step 1: Identify the Data 155
- Physical Log Buffer 157
- Double Buffering 158
- Causes of Flushing 158
- Flushing a Full Buffer 159
- Logical Log Buffer 160
- Buffer Contents 162
- OnLine Checkpoints 164
- Fast Recovery 165
- Archive Checkpoints 165
- U-L) and frees 166
- System Architecture 2-73 167
- MLRU queues reaches 168
- System Architecture 2-75 169
- LRU write 169
- Sorted Write 170
- Idle Write 170
- Foreground Write 171
- LRU Write 171
- Chunk Write 171
- Writing Data to a Blobspace 172
- Disk Data Structures 175
- I/O is done in units of 176
- BUFFSIZE in the configuration 176
- Blobpage 178
- Dbspace and Blobspace 178
- Database 179
- Tblspace 179
- Physical Log 180
- Logical Log 180
- Structure of the Root Dbspace 181
- ■ Unused pages 183
- Structure of a Blobspace 185
- OnLine Limits for Chunks 187
- Reserved Pages 189
- PAGE_CKPT 191
- PAGE_PZERO 191
- PAGE_CONFIG 191
- PAGE_DBSP 193
- PAGE_PCHUNK 194
- PAGE_MCHUNK 195
- PAGE_ARCH 196
- Chunk Free-List Page 197
- Tblspace Number 199
- Database Tblspace 201
- SQL statement 202
- DATABASE 202
- Allocate Disc Space 203
- Track Systems Catalogs 203
- OnLine Limits for Databases 204
- Placement 207
- Tracking 207
- Structure of an Extent 208
- Page Types 209
- Next Extent Allocation 211
- Structure of a Dbspace Page 214
- Page Header 215
- Timestamp 215
- Slot Table 215
- Data Row Format and Rowid 217
- System Architecture 2-125 219
- Single-Page Storage 220
- Multipage Storage 221
- Storage of Modified Rows 223
- System Architecture 2-131 225
- Structure of an Index Page 227
- The Root Node Page 228
- Leaf Node Pages 230
- Index Key Entries 232
- Branch Node Pages 235
- 2-Bit Bit-Mapped Pages 237
- 4-Bit Bit-Mapped Pages 238
- Blobspace Page Types 242
- Logical Log Files 248
- File Rotation 249
- File Contents 250
- Number and Size 250
- Blobspace Logging 252
- Long Transactions 253
- Operating OnLine 257
- Operating OnLine 3-3 259
- Changing Modes 262
- Operating OnLine 3-7 263
- DB-Monitor 263
- From Offline to Quiescent 264
- From Offline to Online 264
- From Quiescent to Online 265
- From DB-Monitor 266
- From the Command Line 266
- Logical Log Administration 269
- Your Configuration File 270
- Logical Log File Backups 270
- Freeing the Logical Log Files 271
- Configuration Parameters 272
- LTAPEBLK and LTAPESIZE 273
- Location of Logical Log Files 274
- Preliminary Consideration 275
- Logical Log File Status 282
- Logical Log File ID Numbers 283
- Add a Logical Log File 284
- Drop a Logical Log File 286
- ■ End logging for a database 289
- Adding Logging to a Database 290
- Back Up a Logical Log File 292
- Free a Logical Log File 295
- DB-Monitor Force 298
- Archive Administration 299
- Archive Types 300
- Level-0 Archive 300
- Level-1 Archive 301
- Level-2 Archive 301
- Incremental Archive Strategy 301
- Plan the Archive Schedule 303
- Minimize Restore Time 304
- Minimize Archive Time 305
- Online Archives 305
- Single Tape Drive 305
- Operator Availability 306
- The Archives 307
- TAPEBLK and TAPESIZE 308
- Preliminary Considerations 309
- Create an Archive, Any Type 313
- Two Tape Drives 315
- One Tape Drive 316
- Monitor OnLine Activity 317
- Monitor Archive History 318
- Monitor Blobs in a Blobspace 319
- Monitor Blobs in a Dbspace 321
- Monitor Buffers 322
- Monitor Buffer-Pool Activity 324
- Monitor Checkpoints 325
- Monitor Chunks 326
- Monitor Databases 330
- Monitor Dbspaces 331
- Monitor Disk Pages 333
- Monitor Extents 334
- Monitor Index Information 335
- Monitor Logging Activity 336
- Monitor the Message Log 338
- Monitor OnLine Profile 339
- Monitor Tblspaces 341
- Modify OnLine Configuration 343
- Create a Blobspace 344
- Drop a Blobspace 347
- Add a Chunk 350
- Create a Dbspace 353
- Drop a Dbspace 355
- Enforce/Turn Off Residency 356
- Enable Mirroring 360
- Start Mirroring 361
- End Mirroring 362
- Things to Avoid 372
- Data Consistency, Recovery 373
- Consistency Checking 378
- Using the tbcheck Commands 379
- Using the OnLine Message Log 380
- ISAM error is returned: 381
- DUMPCORE 383
- DUMPSHMEM 383
- Recovering from Corruption 384
- Mirroring 386
- Beginning 387
- Processing 388
- Recovery 389
- OnLine Logging Overview 390
- Dbspace Logging 391
- Operations Logging 396
- Operations Rollback 396
- Blob Restoration 397
- Ready LTAPEDEV 399
- Locate the Next Logical Log 399
- Copy Blobpages 399
- Place Log Header on Tape 400
- Write Log Records to Tape 401
- Write Trailer Page 402
- Mount a Tape on TAPEDEV 403
- Verify the Archive Level 404
- Force a Checkpoint 404
- Purpose of Data Snapshot 405
- Archive Disk Pages 406
- Write Tape Header Page 407
- Archive Reserved Pages 408
- Determine Archive Criteria 409
- Write a Trailer Page 410
- Update the Reserved Pages 410
- Fast Recovery and Logging 412
- Step 1: Checkpoint Condition 413
- Verify OnLine Configuration 420
- Mount Level-0 Archive Tape 421
- Verify Current Configuration 422
- Prompt for Logical Log Backup 422
- Roll Forward Logical Logs 423
- Database and Table Migration 424
- UNLOAD/dbschema/LOAD 426
- UNLOAD/dbschema/dbload 426
- ■ UNLOAD /dbschema /LOAD 432
- ■ UNLOAD /dbschema /dbload 432
- Move Files 433
- Using dbexport and dbimport 434
- Using tbunload and tbload 435
- How to Improve Performance 441
- Disk Layout 444
- Blobpage Average Fullness 447
- Apply Effective Criteria 448
- When Is Tuning Needed? 450
- Bufsize Pages/IO Fields 451
- Shared-Memory Buffers 453
- Shared-Memory Resources 454
- Log Buffer Size 455
- How Is Tuning Done? 456
- Page-Cleaner Parameters 457
- Efficient Page Cleaning 458
- Checkpoint Frequency 460
- How Psort Works 462
- Tuning Psort 463
- Psort and Shared Memory 464
- DB-Monitor Screens 467
- Main Menu 470
- Status Menu 471
- Parameters Menu 472
- Dbspaces Menu 473
- Mode Menu 474
- Force-Ckpt Option 475
- Archive Menu 476
- Logical-Logs Menu 477
- Utilities 479
- Utilities 7-3 481
- ■ Lock mode 484
- Destination Options 485
- Contents of the Schema File 487
- ■ Invalid command parameters 489
- Input File Location Options 490
- Create Options 492
- Utilities 7-15 493
- ASCII files into one or 493
- LOAD statement: 493
- ASCII input files 493
- IBM Informix 494
- Utilities 7-17 495
- Command-File Syntax Check 496
- Starting Line Number 496
- Batch Size 497
- Bad-Row Limits 498
- How to Create a Command File 499
- Delimiter Form FILE Statement 500
- ■ Save the output to a file 510
- Include Synonyms 511
- Include Privileges 512
- Option Descriptions 517
- -cd and -cD Options 518
- -ce Option 518
- -ci and -cI Options 518
- -cr Option 519
- -n Option 519
- -pB Option 520
- -pc Option 520
- -pd and -pD Options 520
- -pe Option 521
- -pp and -pP options 521
- -pr Option 522
- -pt and -pT Options 522
- -q Option 523
- -y Option 523
- No Options 524
- -i Option 524
- -p Option 525
- -s Option 525
- DBA privilege for the 526
- Specify Tape Parameters 527
- Utilities 7-51 529
- Log-Record Read Filters 530
- -d Option 531
- Log-Record Display Filters 532
- Interpreting tblog Output 533
- Record Types 534
- Record Contents 535
- Utilities 7-65 543
- Change OnLine Mode 544
- Switch the Logical Log File 546
- Kill an OnLine Server Process 547
- Kill an OnLine Transaction 547
- Utilities 7-73 551
- Create a Blobspace or Dbspace 552
- Drop a Blobspace or Dbspace 553
- Change Chunk Status 555
- Utilities 7-81 559
- -B Option 562
- -c Option 562
- -D Option 564
- -F Option 565
- -k Option 566
- -l Option 567
- -m Option 569
- -o Option 569
- -P Option 573
- -r Option 573
- -R option 573
- -t Option 576
- -u Option 577
- -X Option 579
- -z Option 580
- Utilities 7-103 581
- Request a Logical Log Backup 582
- Start Continuous Backups 582
- Create an Archive 583
- Perform a Data Restore 583
- Utilities 7-107 585
- DB-Monitor Logical-Logs 585
- OnLine Message Log 589
- Alphabetized Messages 593
- Product Environment 621
- The OnLine Environment 623
- OnLine Features 624
- High Performance 624
- Multimedia Support 625
- Distributed Data Queries 626
- Bad-Sector Mapping 626
- What Is Multiple Residency? 627
- How Multiple Residency Works 630
- SERVERNUM 633
- DBSERVER-NAME 633
- Step 5: Initialize New OnLine 634
- DATABASE stores5@italy 636
- BEGIN WORK 636
- COMMIT WORK 636
- Product Environment 9-19 639
- Protocol Components 640
- Example Transaction Commit 641
- Example Transaction Rollback 642
- Coordinator Recovery 643
- SQLEXEC to 644
- Participant Recovery 646
- Product Environment 9-27 647
- TXTIMEOUT. When 647
- Presumed-Abort Optimization 649
- Product Environment 9-31 651
- Product Environment 9-33 653
- Figure 9-8 653
- Product Environment 9-35 655
- Figure 9-9 655
- Heuristic Rollback 656
- Heuristic End-Transaction 660
- Product Environment 9-43 663
- IBM Informix STAR 664
- TABLOCKS 665
- ENDTRANS 665
- Transaction Commit Records 666
- Heuristic Rollback Records 668
- Product Environment 9-53 673
- HEURTX recordassociated with 674
- Example Manual Recovery 675
- DEADLOCK TIMEOUT 677
- TXTIME-OUT 678
- Tracking a Global Transaction 679
- Transaction address Field 679
- Transaction flag Field 680
- Transaction user Field 681
- Transaction locks Field 681
- Transaction log begin 681
- Transaction isolation Field 682
- Transaction retries Field 682
- Transaction coordinator Field 682
- Appendix 683
- Notices A-3 685
- COPYRIGHT LICENSE: 685
- Trademarks 686
- Index 11 697
- Index 13 699
- Index 15 701
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