TransactionOriented Checkpoint TOC

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Transaction-Oriented Checkpoint (TOC)

• Frequently used pages need to be written out each
  time a transaction commits
• Not suitable for large applications

Source T. Haerder, A. Reuter
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Transaction-Consistent Checkpoint (TCC)
Source T. Haerder, A. Reuter
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Transaction-Consistent Checkpoint (TCC)

• Represents a state when no update transactions
  are active
• When checkpoint generation is triggered
• All new update transactions are put on hold
• All incomplete update transactions are completed
• Write out all modified pages
• Drawback
• Delay new update transactions not suitable for
  large multi-user DBMS
• High checkpointing costs

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Action-Consistent Checkpoint (ACC)
Source T. Haerder, A. Reuter
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Action-Consistent Checkpoint (ACC)

• Represents a state between complete update
  actions
• When checkpoint generation is triggered
• All new actions are put on hold
• All incomplete actions are completed
• Write out all modified pages
• Less disruptive than TCC
• Still costly when buffers are large

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Fuzzy Checkpointing

• Represents a state which does not satisfy any
  consistency constraints.
• Dumps out the modified data to nonvolatile
  storage without quiescing normal transaction
  activities