Real Application Cluster — > ASM
How error look like in Database Alert log :
WARNING: Read Failed. group:1 disk:4 AU:11852 offset:892928 size:8192
WARNING: failed to read mirror side 1 of virtual extent 1722 logical extent 0 of file 285 in group [1.4277692974] from disk DATA01_0004 allocation unit 11852 reason error; if possible,will try another mirror side
Errors in file /home/app/oracle/diag/rdbms/absnl/ABSNL1/trace/ABSNL1_ora_24108.trc:
WARNING: Read Failed. group:1 disk:4 AU:11852 offset:892928 size:8192
WARNING: failed to read mirror side 1 of virtual extent 1722 logical extent 0 of file 285 in group [1.4277692974] from disk DATA01_0004 allocation unit 11852 reason error; if possible,will try another mirror side
For the First time when I see this error i thought i had problem in my storage (ASM) But after checking And everything was Ok i start search at Http://Support.oracle.com
Yes it’s Bug , and the Bug Number is 10422126.
you can Check Some Notes related to this issue which You should download Patch and apply it or upgrade to 11.2.0.3
WARNING: Failed To Read Mirror Side 1 continuously reported in the alert log [ID 1289905.1]
WARNING: failed to read mirror side 1 of virtual extent ….. [ID 1274852.1]
Thank you
Osama Mustafa
Technology Geek 
Thanks Osama
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Welcome my friend 🙂
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HI Osama, My database version is 12.1.0.2.0, still I see this error in alert log. Do you say still this bug is not fixed ?RegardsShaik Zabiulla
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Seems no, but you can review document Huge number of alert log entries: 'WARNING: IO Failed…' 'WARNING: failed to read mirror side 1 of virtual extent …' (Doc ID 1274852.1) there is workaround that will help you .. hopefully otherwise you have to open SR … Good Luck
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