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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
ID: 18851627
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
gattu007 earned 200 total points
ID: 18851659
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
ID: 18851868
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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Expert Comment

by:mohammadzahid
ID: 18852741
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
ID: 18852743
sorry, I meant to say 2 members for a redo log group ..

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Author Comment

by:jung1975
ID: 18853038
thanks.. what is member?
Log1A  --> is this one member?
Log1B  -

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Author Comment

by:jung1975
ID: 18853109
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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mohammadzahid earned 300 total points
ID: 18853558
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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