Oracle Internals Notes

Log Entry Prebuilding

Prior to Oracle release 8.1, the component change vectors for redo entries larger than the value of the _log_entry_prebuild_threshold parameter would first be copied into a temporary buffer in the PGA of the process, before acquiring any redo latches, so that they could be copied into the log buffer in a single operation. This was reflected in the redo entries linearized statistic. The intent was to reduce the duration for which the redo copy latches were held for large copies, because LGWR was sensitive to redo copy latch availability. From release 8i, LGWR no longer needs to take the redo copy latches and so prebuilding is obsolete.

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12-Oct-2007 22:22
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