Recovery Algorithms: RDU vs RIU
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Timeè t1 t2 t3 t4
checkpoint checkpoint checkpoint system crash
2.1 Describe the recovery needed according to the RDU (Recovery using Deferred Update) algorithm. You must indicate which transactions need to be undone/redone and which are ignored and need to be restarted. (2.5 points)
T4 and T5 are ignored because they did not reach their commit points. They need to be restarted.
T2 must be REDONE because it was committed after the last checkpoint.
2.2 Repeat the previous question using the RIU (Recovery using Immediate Update) algorithm. (2.5 points)
T4 and T5 are UNDONE because they did not reach their commit points and need to be restarted.
T2 must be REDONE because it was committed after the last checkpoint.