Oracle Redo Log Corruption

Posted by PDSERVICE on Nov 13, 2015 In

Block corruption in redo log file blocks. Can be a logical or a physical corruption
Invalid block in redo log
ORA-353 log corruption near block %s change %s time %s
ORA-368 checksum error in redo log block
ORA-355 change numbers out of order

DIAGNOSTIC ANALYSIS:

--------------------

Alert log hits the error:

ORA-00353: log corruption near block 6071112 change 65773130219520 time

08/22/2012 12:59:45

ORA-00312: online log 7 thread 1: '/oradata5/mefdbprd/redo07b.log'

ORA-00312: online log 7 thread 1: '/oradata5/mefdbprd/redo07.log'

Incident trace file does not dump the bad redo

Customer's redo validate does not throw any error

Customer can stop and restart the capture

which means it is not a ondisk corruption

It looks like the corruption is still in cache

WORKAROUND:

-----------

Maybe same as original bug# 13840711

which is _redo_read_from_memory = FALSE

When this bug is encountered during media recovery (or by dumping the corrupt

archived log), errors similar to the following will be reported:

ORA-00354: corrupt redo log block header

ORA-00353: log corruption near block 257 change 6895 time 01/14/98 14:09:17

ORA-00334: archived log: '/users1/oracle73/arch/arc90.arc'

Because the bug causes chunks of blocks to be written to the wrong location,

the logical block number (recorded in each redo block header) will be out

of sequence. In a healthy archived log, the logical block numbers matches

the relative block location in the file.

So, the steps required to determine whether bug 554516 is the cause of the

corruption are:

1. Ask the customer to hex dump the offending redo block, and a few blocks

either side of it. Then email the trace file to Support. In the above

example:

% dd if=/users1/oracle73/arch/arc90.arc bs=512 skip=255 count=6 | od -x >

archlog.hex

The above command will dump block number 257 (reported in the ORA-353) and

a few blocks either side.

2. In a redo log, the first ub4 field is the log sequence number. The second

ub4 is the logical block number.

Note:

Redo logs are written in O/S size blocks. Verify the size of the redo log

block before issuing the dd comma

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