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Talk:Algorithms for Recovery and Isolation Exploiting Semantics

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Redo

Why does the ARIES redo all tansactions and not only the commited ones? 212.25.82.123 (talk) 11:10, 1 November 2010 (UTC)[reply]

See What is the benefit of repeating history in ARIES recovery method? Franck Dernoncourt (talk) 03:24, 9 April 2013 (UTC)[reply]

Redo

The article claims the following:

If page P exists in the DPT table, then we see whether the Sequence Number in the DPT is smaller than the Sequence Number of the log record (i.e. whether the change in the log is newer than the last version that was persisted). If it isn't, then we don't redo the entry since the change is already there. If it is, we fetch the page from the database storage and check the Sequence Number stored on the page to the Sequence Number on the log record. If the former is smaller than the latter, the page does not need to be written to the disk.

The last sentence seems wrong to me. Shouldn't this be the other way around? In case the Sequence Number stored on the page is older than the Sequence Number on the log the page needs to be written to disk. Mohlerm (talk) 08:43, 9 August 2015 (UTC)[reply]

The article claims the following:

Every time a transaction begins or commits we write a "Begin Transaction" entry or an "End Of Log" entry for that transaction respectively.

But in the original paper there's nothing like explicit "Begin Transaction" except for 2PC transactions, which is "Prepare" record.

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