Consider this set of 4 transactions and system log.What needs to be done about transactions T1, T2,
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Consider this set of 4 transactions and system log.What needs to be done about transactions T1, T2, T3, T4 during recovery?
| T1 | T2 | T3 | T4 |
|---|---|---|---|
| read_item(A) | read_item(B) | read_item(A) | read_item(B) |
| read_item(D) | write_item(B) | write_item(A) | write_item(B) |
| write_item(D) | read_item(D) | read_item(C) | read_item(A) |
| write_item(D) | write_item(C) | write_item(A) | |
[start_transaction, T1] [write_item, T1, D, 20] [commit, T1] [checkpoint] [start_transaction, T4] [write_item, T4, B, 15] [write_item, T4, A, 20] [commit, T4] [start_transaction, T3] [write_item, T3, A, 30] [write_item, T3, D, 25] ** system crash **
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