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Extended ephemeral logging (XEL) is a more general variation of the ephemeral logging (EL) technique for managing a log of database activity on disk; it does not require a timestamp to be maintained with each object in the database. XEL does not require periodic checkpoints and does not abort lengthy transactions as frequently as traditional firewall logging for the same amount of disk space. Therefore, it is well suited for concurrent databases and applications which have a wide distribution of transaction lifetimes.Simulation results indicate that XEL can offer significant savings in disk space, at the expense of slightly higher bandwidth for logging and more main memory. The reduced size of the log permits much faster recovery after a crash as well as cost savings. |
