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Mirror online redo log files

Posted on 2007-04-04
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How can I mirror the online redo log files for the best backup/recovery practice?  can you show me some examples?
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Question by:jung1975
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by:gattu007
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try keeping the members in different disks... or may be on RAID...

Using OFA is recommended if the machine on which you plan to create the database has a different directory structure. Standard file paths can be used if the target machine has a similar directory structure.
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by:gattu007
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The number of disks for redo logs is mostly determined by the redo log size, which is generally small compared to current technology disk sizes. Typically, a configuration with two disks (possibly mirrored to four disks for fault tolerance) is adequate. In particular, by having the redo log files alternating on two disks, writing redo log information to one file does not interfere with reading a completed redo log for archiving.

Mirroring can cause I/O bottlenecks. Generally, the process of writing to each mirror is done in parallel and does not cause a bottleneck. However, if each mirror is striped differently, then the I/O does not complete until the slowest member of the mirror is complete. To avoid I/O problems, stripe the copies using the same number of disks as used for the primary database.

http://download-east.oracle.com/docs/cd/B10501_01/server.920/a96533/iodesign.htm#22610
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by:jung1975
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I have currently all the log files in E: which is RAID 5 .. log1A, log1B, log2A, Log2B, Log3A, Log3B, Log4A, Log4B, etc...

So is it a good idea to move all of Log B group to different disk ( F:) ? I am not quite sure how to do this...
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by:mohammadzahid
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You can do this by using mutilplexing redo logs.  

For example:

If redo log group have 1 members then you can put each members on seperate disk.

Please goto this url for steps:

http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b10739/onlineredo.htm

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by:mohammadzahid
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sorry, I meant to say 2 members for a redo log group ..

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by:jung1975
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thanks.. what is member?
Log1A  --> is this one member?
Log1B  -

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by:jung1975
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actually, if there are more than one online redo log  group( for example, log1A, Log1B, Log2A, Log2B, etc...), the online log files are already multiplexed..right?
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not necessary. You can check the location of the logfiles by running select against V$LOGFILE and check locations of the members.
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