A look into oracle redo, part 11: log writer worker processes
Starting from Oracle 12, in a default configured database, there are more log writer processes than the well known ‘LGWR’ process itself, which are the ‘LGnn’ processes: $ ps -ef | grep test | grep lg...
View Article18c: some optimization about redo size
Some years ago, at the time of 12.1 release, I published in the SOUG newsletter some tests to show the amount of redo generated by different operations on a 10000 rows table. I had run it on 12.2...
View ArticleIndex Splits – 3
This is stored only for reference, and in case anyone wants to wade through the details. It’s the redo log dump from the 90/10 index leaf block split test from the previous blog posts running on...
View ArticleDump logfile
Here’s a little procedure I’ve been using since Oracle 8i to dump the contents of the current log file – I’ve mentioned it several times in the past but never published it, so I’ll be checking for...
View ArticleRedo Dumps
A thread started on the Oracle-L list-server a few days ago asking for help analysing a problem where a simple “insert values()” (that handled millions of rows per day) was running very slowly. There...
View ArticleQuiz Night
Upgrades cause surprises – here’s a pair of results from a model that I constructed more than 15 years ago, and ran today on 12.2, then modified and ran again, then ran on 11.2.0.4, then on 12.1.0.2....
View ArticleUpdate restarts
Somewhere I think I’ve published a note about an anomaly that’s been bugging me since at least Oracle 10g – but if it is somewhere on the Internet it’s hiding itself very well and I can’t find it,...
View ArticleNologging
Bobby Durrett recently published a note about estimating the volume of non-logged blocks written by an instance with the aim of getting some idea of the extra redo that would be generated if a database...
View ArticleFlashback Bug
Here’s a problem with the “flashback versions” technology that showed up at the end of last week. There’s a thread about it on the Oracle Developer community forum, and a chain of tweets that was my...
View ArticleQuiz time
Here’s a fun little item that I’ve just rediscovered from 2016.There’s a fairly commonly cited query that aggregates and tabulates the first_time column from the v$log_history view by hour of day,...
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