Tales From A Lazy Fat Oracle DBA

$ prashantdixit/oracle90@ace as sysdba

  • Likes

    • 86,065
  • Archives

  • ΰ₯

  • Categories

  • Cause I Support!!

  • SoundCloud

  • Subscribe

  • Few Favorites

  • Prashant Dixit is the FatDBA

  • Follow Tales From A Lazy Fat Oracle DBA on WordPress.com
  • My Twitter Feeds

  • Oracle Radio

  • Magic Of Oracle

  • Disclaimer!

    FatDBA or Oracle 'Ant' is an independent web-blog/site.The experiences, Test cases, views, and opinions expressed in this website are my own and does not reflect the views or opinions of my employer.

    This site is independent of and does not represent Oracle Corporation in any way. Oracle does not officially sponsor, approve, or endorse this site or its content.
    Product and company names mentioned in this website may be the trademarks of their respective owners.

Number Of Oracle Database 12c Log Writers ? Yes Finally, but boon or bane ?

Posted by FatDBA on August 4, 2016

Was really excited when I saw on my 12c test machine by default it had two redo workers in addition to the “parent” log writer.

a877463c8ff55d5dbd531826356d319c

Snippet from one of the test database with a parent and two redo workers.

$ ps -eaf|grep tunedb | grep ora_lg
oracle 54964 1 0 14:37 ? 00:00:00 ora_lgwr_tunedb
oracle 54968 1 0 14:37 ? 00:00:00 ora_lg00_tunedb
oracle 54972 1 0 14:37 ? 00:00:00 ora_lg01_tunedb

Yes, with 12c the wait is over. πŸ™‚ πŸ™‚ πŸ™‚ πŸ™‚
Multiple LGWRs is great news because serialization is the demise of computable processes and structures.

But But But —- Not sure how stable and good this feature is. I recently faced one bug 19181582 : DEADLOCK BETWEEN LG0N ON ‘LGWR WORKER GROUP ORDERING’ in 12c production environment because of this new feature.
It causes the database to hang and at this moment the patch is not ready.

Solution is to set instance parameter _use_single_log_writer=TRUE, with this parameter I was able to REDUCE the number LGWRs to only one.

Right now understanding to control the number of log writer slave with _max_outstanding_log_writes and _max_log_write_parallelism instance level parameters or any AUTO Behaviors of increasing-decreasing redo writers.

Thanks
Prashant Dixit

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: