CS655-HessahAlsaaran-DBonS3

What if the pending update has not been performed

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Unformatted text preview: and vulnerable to failure. (could use scheduler) Ê༌  No need for locks. should be applied. Ê༌  Each client has a local queue of commit log records (ATOMIC queue). Ê༌  Readers and Writers (Clients). Ê༌  Each page has a header, and each B- tree’s root node metadata à༎ contain last update timestamp. Ê༌  When logging or reading à༎ check timestamp. Ê༌  Trade- off between cost and fast updates in setting time threshold. Ê༌  Additional information: commit/transaction id. Ê༌  Log records are sent to the PU queue, then deleted from ATOMIC queue. Ê༌  In the case of client failure, it will check the ATOMIC queue when it restarts. Ê༌  What if the client does not restart? They ensured the “all” part, but not the “none” part. 15 16 Client- Side Consistency Models Client- Side Consistency Models Ê༌  Monotonic Reads Ê༌  Read your writes Ê༌  If x have been read, any successive read must result in the same vale or a newer value. Ê༌  Clients maintain information about past cached pages timestamps. Ê༌  Monotonic Writes Ê༌  A write on x is completed before any successive writes. Ê༌  Preserve order per client using counters. Ê༌  (Client id, counter value) is added to the log record, and in the header of the updated page reflecting the clients last update. Ê༌  During checkpoint, out- of- order logs are detected and unprocessed. 17 Ê༌  A local write on x will be seen by a successive read. Ê༌  Local updated copy. Ê༌  What if the pendi...
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