datafiles and redo logs on the same drive

Hi guys,.

http://docs.Oracle.com/CD/E11882_01/server.112/e25494/onlineredo002.htm#i1306224

>

Data files should also be placed on different disks of redo log files to reduce contention in writing of the data blocks and redo records.
>

I really think if he actually any challenge when the first of all oracle can only writes files 1 redo log at a time.
http://docs.Oracle.com/CD/E11882_01/server.112/e25494/onlineredo001.htm
>
Database only Oracle uses redo log files at the same time to store redo records written since the restore log buffer by progression. Log roll forward LGWR is preparing actively to is called the log during recovery.
>

If the process flow, I got after reading the chapters is

When LGWR fills a log file of redo (roll forward records) then there will be a log switch + control points where writing for data blocks occur. There seems to be a flow series rather than a simultaneous sort of flow. So I don't really understand it when he speaks of contention will take place when records of data and files written redo which is the redo log file are on the same disks.

Just to confirm with you guys, whenever there is a switch of newspaper one point of control occurs too right.
http://docs.Oracle.com/CD/E11882_01/server.112/e25494/onlineredo002.htm? You can search checkpoint to access the section she made mention of this documentation.

Think about this:

Restore means to keep the information around in case you need to re-do (recovery or standby mode, i.e. the continuous collection). Updates as you do in a broad sense will be so potentially being twice, once for the data files and once to do it again. I'm sure you understand that the data is written in memory, and then later to the data by the writer of the db files, while there could be many more group of writing data, or they may even be long delayed. In addition, the data files are read at random, so you can't really think again in series compared to the data. Do it again is series, archiving is set, but the data is random, and random how depends on how your system is used.

So that means all the type of reads and writes per redo and archive is fundamentally different from data and cancel. In the first case, you want to be able to breath out as I/O that you can, for the latter, you want to be able to randomly reading or writing at different times, with Oracle being smart enough to do a bit of it in memory and optimistic enough to make assumptions on when to do things and quite lazy for not doing everything right. Roll forward is critical.

A while ago, someone pointed out that the e/s modern buffered in memory, do not really worry about this, because all the work required to set up and maintain it after spending records, fees are not much better than striping and mirroring everything (you can google SAMI). This is true to a point, and we can debate endlessly about RAID types and their effects on performance and how their buffering makes [url http://www.baarf.com/] useless BAARF. But the real debate is, where is the point that you should use separate to redo and data devices? In the real world, we often receive a standard hardware configuration, which works very well until it's not. A disk or controller will puff in a RAID-5 can happen "is not" real quick.

You should probably take two thoughts:

The docs are pretty General, and some old tips do not apply, may have transformed into myth or perhaps too general to be meaningful.

There is always something in the db, and the more things underway, less you can make generalizations about the serialization.

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