Today?,customer reflect? their a 10.2.0.4 database alert.log has following information:
Thu Dec? 1 17:19:14 2011
Read of flashback database logfile 72,block 121492 found corrupted data.
See trace file for more information.
Reread of flashback database logfile 72,block 121492 found valid data.
Read of flashback database logfile 72,block 121507 found corrupted data.
See trace file for more information.
Reread of flashback database logfile 72,block 121507 found valid data.
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Search the matelink,gaves the answer:
Read Of Flashback Database Found Corrupted Data / Reread Found Valid Data [ID 554561.1]
Applies to:
Oracle Server - Enterprise Edition - Version: 10.2.0.2 and later?? [Release: 10.2 and later ]
Information in this document applies to any platform.
Symptoms
The below mentioned messages would be seen in the alert.log file.
Read of flashback database logfile 821,block 534 found corrupted data.
Flashback Database log 821 thread 1 seq = 163037:
/b001/oradata/p933/archlog_backup/DG_P933/flashback/o1_mf_3pfq3dsc_.flb
Corrupt flashback block: error 1
Block 534,Size 16384,BlockHeader:
Seq: 161889 Block: 534 Cks: 0x749f Flag: 0x1 Lst: 120
Reread of flashback database logfile 821,block 534 found valid data.
Read of flashback database logfile 821,block 545 found corrupted data.
Need to verify the cause of the error.
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Cause
The cause of the issue is due to the unpublished internal Bug 6033541 which has been fixed in the version 11.1
Abstract:? INTERMITTENT CORRUPT BLOCK READS FROM FLASHBACK LOGS
Impact : Nill / No impact
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Solution
No action is required,these error messages can be ignored.
When the view v$flashback_database_log is queried it fetches the information from the flashback block when it is being written,as a result of which we see a fractured block but reread always succeeds.
Oracle writes a message in alert about the initial bad read and the successful reread.
The Bug fix will? stop writing these messages into the alert.log and the trace file if the reread is sucessfull.
