The same arguments used for multiplexing of control files apply
here. However, though you can rebuild the static part of a control file if you lose it,
there is no way to reproduce a lost redo log file. So, be sure to have multiple copies
of the redo file. Simple redundant disk protection is not sufficient for cases in which
human error results in the corruption or deletion of a redo log file.
Oracle writes synchronously to all redo log members. Oracle will wait for confirmation
that all copies of the redo log have been successfully updated on disk before the
redo write is considered done. If youpu t one copy on a fast or lightly loaded disk,
and one copy on a slower or busier disk, your performance will be constrained by the
slower disk. Oracle has to guarantee that all copies of the redo log file have been successfully
updated to avoid losing data.
Consider what could happen if Oracle were to write multiple redo logs asynchronously,
writing to a primary log and then updating the copies later in the background.
If a failure occurs that brings the system down and damages the primary log, Oracle
might not have completed updating all the logs.
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