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Re: DB redolog




Hi Frank,

On 12/17/2014 2:11 AM, xiangdongzou wrote:
HI all:

        As we know,when we shutdown the database cleanly,the database can
do a checkpoint.So we don't need redo log againg.In mysql(innodb),we can
restart normaly.But oracle database also need redo log group(current), why?



While someone on this list probably knows the answer to your question, this list is in support of the MySQL database system and its related products. As you correctly identified, the InnoDB storage engine starts back up without any problems.

In fact, the REDO log is there for recovery purposes only. During a normal startup following a normal or slow shutdown, it is not required at all. During a recovery restart, any transactions that were logged but not yet checkpointed into the physical data file(s) are handled then. This gives us the best chances of reaching a fully consistent state after some kind of dirty shutdown event (crash, power failure, disk failure, ...)

This link describes the method that must be followed in order to erase the logs to allow the server to generate new ones on the next restart. This is usually done to change the size, number, or location of the REDO log files.
http://dev.mysql.com/doc/refman/5.6/en/innodb-data-log-reconfiguration.html

Please let us know if you have any other questions about MySQL.

Yours,

--
Shawn Green
MySQL Senior Principal Technical Support Engineer
Oracle USA, Inc. - Hardware and Software, Engineered to Work Together.
Office: Blountville, TN

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