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Physical Logging, Checkpoints, and Fast Recovery

In This Chapter
Critical Sections
Physical Logging
Fast Recovery Use of Physically-Logged Pages
Backup Use of Physically-Logged Pages
Database Server Activity That Is Physically Logged
Physical Recovery Messages
Physical Logging and Simple Large Objects
Physical Logging and Smart Large Objects
Size and Location of the Physical Log
Specifying the Location of the Physical Log
Estimating the Size of the Physical Log
Configuring the Size of the Physical Log
Physical-Log Overflow When Many Users Are in Critical Sections
Effect of Checkpoints on the Physical-Log Size
Physical-Log Overflow When Transaction Logging Is Turned Off
Details of Physical Logging
Checkpoints
Full Checkpoint
Fuzzy Checkpoint
Fuzzy Operations
Write-Ahead Logging and Fast Recovery
Fuzzy Checkpoints Improve Performance
Events That Initiate a Fuzzy Checkpoint
Events That Initiate a Full Checkpoint
Sequence of Events in a Checkpoint
User Threads Cannot Enter a Critical Section
Logical-Log Buffer Is Flushed to the Logical-Log File on Disk
The Physical-Log Buffer is Flushed to the Physical Log on Disk
Modified Pages in the Buffer Pool Are Flushed to Disk
Checkpoint Thread Writes Checkpoint Record
Physical Log Is Logically Emptied
Backup and Restore Considerations
Fast Recovery
Need for Fast Recovery
Situations When Fast Recovery Is Initiated
Fast Recovery and Buffered Logging
Possible Physical Log Overflow During Fast Recovery
Fast Recovery and No Logging
Details of Fast Recovery After A Full Checkpoint
Returning to the Last-Checkpoint State
Finding the Checkpoint Record in the Logical Log
Rolling Forward Logical-Log Records
Rolling Back Incomplete Transactions
Details of Fast Recovery After A Fuzzy Checkpoint
Returning to the Last-Checkpoint State for Nonfuzzy Operations
Locating the Oldest Update in the Logical Log
Applying the Log Records for Fuzzy Operations
Rolling Forward Logical-Log Records
Rolling Back Incomplete Transactions
Alternative Fast Restart Recovery Options for Fuzzy Operations
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