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Home > Archive > Oracle certifications > April 2002 > Multiplexing of redo log files..
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Multiplexing of redo log files..
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| rohit1346 2002-04-09, 7:18 am |
| My question is regarding the multiplexing of redo log files.Suppose we create 2 groups and have 2 members in each group, so in all we have 4 files..
group 1 ) file 1 , file 2
group 2 ) file 1 , file 2
Now, if LGWR fails to write to both files of group 2, then database will crash, my question is ... why can't the other group can take over and act independently and prevent database from crashing? | |
| laloca 2002-04-13, 5:31 pm |
| Hi rohit1346,
the redo log groups are written in a circular way, thats the reason why you need at least two redo log groups. 
A redo log group can consist of one ore more members. Put them always on different disks to avoid losing all members of a log group at once:
Loggroup DiskA DiskB DiskC
Group 1 redo1a.log redo1b.log redo1c.log
Group 2 redo2a.log redo2b.log redo2c.log
Group 3 redo3a.log redo3b.log redo3c.log
if a log switch occurs the redo log group switches. multiplexing means that more than one redolog-file of a redo log group is written parallely to increase security.
if you loose one disk - the database will not stop, because there are two other members to proceed.
hope that helps, | |
| Nirmal 2002-04-17, 1:33 am |
| Hi ,
pls note that DB will not crash ..but it will
hang !
regards
-Nirmal |
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