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Connor McDonald

Thanks for the question, Nery.

Asked: March 27, 2018 - 6:13 pm UTC

Last updated: March 28, 2018 - 5:51 am UTC

Version: 11.2.0.3.0

Viewed 1000+ times

You Asked

Hello Tom,

I currently have 6 log groups of 1 2GB member. These six groups are on the same mount point in a virtual environment. There is a log switch every hour. During peak times, however, the log file sync wait seems to be an issue for us. The mount point where these six files are on have a RAID 5.

Our redo log buffer is currently at 72089600 bytes.

Do I have too many redo logs? Is the buffer too large?

Thanks,


Nery.

and Connor said...

Here's a simplified version of what's going on:

- Your session does "commit"
- It is now waiting on "log file sync"
- Now LGWR must flush the redo buffer to disk
- The I/O time for this will be "log file parallel write"
- Now LGWR is done, your session is notified
- Your session is back running again

Now take a look here

https://asktom.oracle.com/pls/apex/asktom.search?tag=log-file-sync-201603

https://asktom.oracle.com/pls/apex/asktom.search?tag=how-can-we-reduce-wait-event-log-file-sync

which explains why it could be an I/O issue but also possibly *not* be an I/O issue.

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