Reliability-Partition

Reliability-Partition - Reliability In case of a crash,...

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Reliability and Partition Types of Failures 1. Node failure 2. Communication line of failure 3. Loss of a message (or transaction) 4. Network partition 5. Any combination of above Reliability In case of a crash, recover to a consistent (or correct state) and continue processing.
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Reliability and Partition Approaches to Reliability 1. Audit trails (or logs) 2. Two phase commit protocol 3. Retry based on timing mechanism 4. Reconfigure 5. Allow enough concurrency which permits definite recovery (avoid certain types of conflicting parallelism) 6. Crash resistance design
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Reliability and Partition Recovery Controller Types of failures: * transaction failure * site failure (local or remote) * communication system failure Transaction failure UNDO/REDO Logs (Gray) transparent transaction (effects of execution in private workspace) Failure does not affect the rest of the system Site failure volatile storage lost stable storage lost processing capability lost (no new transactions accepted)
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Reliability and Partition System Restart Types of transactions: 1. In commitment phase 2. Committed actions reflected in real/stable 3. Have not yet begun 4. In prelude (have done only undoable actions) We need: stable undo log; stable redo log (at commit); perform redo log (after commit) Problem: entry into undo log; performing the action Solution: undo actions ¬ < T, A, E > DO – UNDO UNDO DO – UNDO – UNDO – UNDO --- UNDO
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Reliability and Partition Local site failure - Transaction committed do nothing - Transaction semi-committed abort - Transaction computing/validating
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This note was uploaded on 12/23/2009 for the course DBST 663 taught by Professor Tba during the Spring '09 term at MD University College.

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Reliability-Partition - Reliability In case of a crash,...

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