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Table of Contents v
Chapter 2 System Architecture
In This Chapter .................. 2-7
Initialization ................... 2-7
Initialization Commands ............. 2-8
What Happens During Shared-Memory Initialization . . . 2-10
What Happens During Disk-Space Initialization ..... 2-14
UNIX Kernel and Semaphore-Allocation Parameters .... 2-18
OnLine User Processes ................ 2-22
How User Processes Attach to Shared Memory ...... 2-24
User Processes and Critical Sections.......... 2-28
OnLine User Process Status and States ......... 2-29
OnLine Database Server Process ........... 2-30
Orphaned Database Server Processes ......... 2-31
OnLine Daemon Processes .............. 2-33
tbinit Daemon ................. 2-33
tbundo Daemon ................ 2-34
tbpgcl Daemon ................. 2-34
Shared Memory and Process Communication ........ 2-36
Shared Memory and Buffer Locks .......... 2-38
Managing Shared-Memory Resources ......... 2-39
Shared-Memory Header.............. 2-47
Shared-Memory Internal Tables ........... 2-48
Shared-Memory Buffer Pool ............ 2-55
OnLine LRU Queues ............... 2-57
LRU Queues and Buffer Pool Management ....... 2-58
How a User Process Acquires a Buffer ......... 2-60
Physical Log Buffer ............... 2-63
Logical Log Buffer ................ 2-66
OnLine Checkpoints ............... 2-70
What Happens During a Checkpoint ......... 2-72
When the Daemons Flush the Buffer Pool........ 2-73
How OnLine Synchronizes Buffer Flushing ....... 2-74
Write Types Describe Flushing Activity ........ 2-75
Writing Data to a Blobspace ............ 2-78
Disk Data Structures ................ 2-81
OnLine Disk Space Terms and Definitions ....... 2-81
Structure of the Root Dbspace ............ 2-87
Structure of a Regular Dbspace ........... 2-89
Structure of an Additional Dbspace Chunk ....... 2-90
Structure of a Blobspace .............. 2-91