Porsche show in Charlotte

Porsche show in Charlotte
Originally uploaded by jmourik

Flashback database impact

Ran into this interesting problem not too long ago. A procedure doing an insert and a merge ran much slower in one environment compared to another similar environment. After tracing in the slow environment and profiling the trace, this came up:



That much time spend on "db file sequential read" for a straightforward "insert into ... values (....)"? Weird...
A bit more investigation showed that lots of those waits were for the undo tablespace:
p5skew --name="db file sequential read" --group=$p1 xxxxx_ora_13766882.trc



So what are those files?

select file_id, tablespace_name from dba_data_files where file_id in (116,179,124,2,115,187,244);

FILE_ID TABLESPACE_NAME
244     UNDO2
179     xxxxx_DAT_IOT
187     UNDO2
124     UNDO2
116     UNDO2
115     UNDO2
2       UNDO2

So mostly undo (83.6%)! Why?

Then I started thinking about one major difference between the two databases, the one with the slow performance had flashback database enabled. A quick search on Metalink gave me Note:565535.1 "Flashback Database Best Practices & Performance". This note tells us that "Insert intensive batch jobs may be impacted by as much as 30% with flashback database on."
So we disabled flashback database, reran the proc and performance improved dramatically. So Oracle was absolutely telling us the truth in that note. So beware of this in Oracle 10g, when using this very cool feature!

PS. Screenshots are from Hotsos profiler output.

Kindle

From looking at this page you might notice I've been having way too much fun with my Kindle and book sites Shelfari and LibraryThing. I got my Kindle a week ago, after long deliberation. Actually, I ordered one last December, but canceled after a month because they weren't in stock. Now I finally ordered again, and so far I'm loving it!
The pics show the size of the Kindle, not too big, easy to hold.
One lesson I learned so far: do NOT leave your Kindle connected to your PC through the USB cable, it will totally drain the Kindle's battery! Ouch! I figured it would work like my Zune, when connected it charges. But no, not the Kindle...
One of my favorite features so far is the build-in dictionary. Mark a line and click lookup, and the Kindle will search the New Oxford American Dictionary for the words. Very nice indeed!

Paperback vs. Kindle vs. CD:



Kindle side view compared to a paperback: