1. CS 632 Lecture 6
Recovery
Principles of Transaction-Oriented Database Recovery
Theo Haerder, Andreas Reuter, 1983
ARIES: A Transaction Recovery Method Supporting Fine-Granularity Locking and Partial Rollbacks Using Write-Ahead Logging
C. Mohan, Don Haderle,
Bruce Lindsay, Hamid Piralesh, and Peter Schwartz, 1992
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2. Principles of Transaction-Oriented Database Recovery
DATABASE RECOVERY: WHAT IT IS EXPECTED TO DO
What Is a Transaction
Which Failures Have To Be Anticipated
Summary of Recovery Actions
THE MAPPING HIERARCHY OF A DBMS
The Mapping Process
The Storage Hierarchy
Different Views of a Database
Mapping Concepts for Updates
CRASH RECOVERY
Dependencies Between Buffer Management and Recovery Component
Classification of Log Data
Checkpoints
ARCHIVE RECOVERY
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3. Atomicity: Consistency: Isolation: Durability: What is a transaction?
actions executed indivisibly
four properties required (the ACID properties):
Atomicity:
all actions in the transaction happen, or none happen
Consistency:
if a transaction preserves the consistency of the DB
Isolation:
execution of one transaction is isolated from that of other transactions
Durability:
if a transaction commits, its effects persist
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4. Which Failures Have to Be Anticipated?
Transaction Failures:
caused by bad input or other violations of consistency
System Failures:
caused by:
bugs in the DBMS code
operating system fault
hardware failure
occur less frequently
Media Failures:
software errors
hardware errors
physical errors
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5. Summary of Recovery Actions
Transaction Undo
when a transaction aborts itself
Global Undo
when recovering from a system failure
incomplete transactions
Partial Redo
complete transactions
Global Redo
archive recovery
full redundancy
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8. Different Views of a Database
Current database
the contents are found on disk or in the DB buffer
Materialized database
the state that the DBMS finds at restart after a crash
Physical database
all blocks of the on-line copy
Three types of update operations:
modification of page contents – affects the current database
write – affects the physical database
propagation – affects the materialized database
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9. Mapping Concepts for Updates
Two schemes for propagation:
Two types of propagation strategies:
ATOMIC
NOT ATOMIC
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10. Dependencies Between Buffer Management and Recovery Component
UNDO Recovery Actions:
STEAL – undo actions necessary
NO STEAL – undo actions not necessary
REDO Recovery Actions:
FORCE – redo actions not necessary
NO FORCE – redo actions necessary
Partial REDO: no logging necessary
Global REDO: logging necessary
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11. Classification of Log Data
Physical State Logging on Page Level
before image – after image
Physical Transition Logging on Page Level
differences between old and new states
Physical State Logging on Access Path Level
Physical/Logical Transition Logging on the Access Path
Logical Logging on the Record-Oriented Level
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12. Checkpoints limit the amount of REDO recovery required after a crash
involve three steps:
write a BEGIN_CHECKPOINT record
write all checkpoint data
write an END_CHECKPOINT record
types:
Transaction-Oriented Checkpoints
Transaction-Consistent Checkpoints
Action-Consistent Checkpoints
Fuzzy Checkpoints
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14. Conclusion taxonomy for classifying the implementation techniques for
database recovery
four criteria:
Propagation
ATOMIC/ NOT ATOMIC
Buffer Handling
STEAL / NO STEAL
EOT Processing
FORCE / NO FORCE
Checkpointing
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16. ARIES – Algorithm for Recovery and Isolation Exploiting Semantics
ARIES: A Transaction Recovery Method Supporting Fine-Granularity Locking
and Partial Rollbacks Using Write-Ahead Logging
ARIES – Algorithm for Recovery and Isolation Exploiting Semantics
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17. Goals Simplicity Operation logging Flexible storage management
Partial rollbacks
Flexible buffer management
Recovery Independence
Logical undo
Parallelism and fast recovery
Minimal overhead
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18. Normal Processing Restart Processing Updates
Total or Partial Rollbacks
savepoints
Transaction Termination
Checkpoints
fuzzy checkpoints
Restart Processing
Analysis Pass
Redo Pass
Undo Pass
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20. Log Records LSN (Log Sequence Number) unique id for each log record
Type
type of record
TransId
id of transaction that wrote the record
PrevLSN
LSN of the previous log record written by the same
transaction that wrote the record
PageID
id of the page referred by the log
UndoNextLSN
present in CLR
Data
redo/undo data describing the update
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21. Page Structure Transaction Table Dirty Pages Table
page_LSN – the LSN of the log record describing the latest
update to the page
Transaction Table
TransId – the id of the transaction
State
LastLSN
UndoNextLSN
Dirty Pages Table
PageId
RecLSN
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22. Restart Processing Analysis Pass Redo Pass Undo Pass
Selective or Deferred Restart
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23. Media Recovery Nested Top Actions
fuzzy image copy (fuzzy archive dump)
image copy checkpoint
media recovery redo point
Nested Top Actions
top actions
nested top actions
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