Franck's Oracle blog
Blog of Franck Pachot, Consultant at dbi services
I'm a Senior Consultant, and Oracle Technology Leader at dbi services (Switzerland).
Certified DBA (OCM 11g, OCP 12c, Performance Tuning Expert, Exadata Implementation) I cover all database areas: architecture, data modeling, database design, tuning, operation, and training.
My preferred area is troubleshooting oracle and performance tuning, especially when I acheive to enable an efficient collaboration between the developers and the
As an Oracle Ace, I participate in the Oracle Community in forums, blogs, articles and presentation. You can follow my activity on this blog: and my twitter account: @FranckPachot
When you migrate, you should be prepared to face some execution plan changing. That's not new. But here I'll show you a case where you have several bad execution plans because lot of histograms are missing. The version is the same. The system is the same. You've migrated with DataPump importing all statistics. You have the same automatic job to gather statistics with all default options. You have repeated the migration several times on a system where you constantly reproduce the load. Have done a lot of regression tests. Everything was ok.
In-Memory Column Store is amazing. It brings very good performance to full table scans. I't easy: just 'flip a switch' and you accelerate all reporting queries on your table, without thinking about what to index and how. But in this post, I would like to warn you about the consequences when you just flip that switch. The new full table scan plan will replace the old ones... even before the table is populated in memory...
I'm not sure that it is the expected behaviour. In my opinion the CBO should consider INMEMORY plans only once the population is done. But here is the exemple.
Before going to the airport to come back in Europe, the las session I assisted at IOUG Collaborate is a panel: Nothing to BLOG About - Think Again
Some famous bloggers were there to help, motivate and inspire people that are afraid to blog. The idea is good. The session was good. The panelists have shared ideas, tips, experience. It was very good.
I'm already a blogger, but that inspired me anyway. In the same idea I'll expose how I started blogging, just in case it gives some ideas.
Note that tomorrow I speak about participating in the community (read, share, write, talk, blog, tweet, link,...) at our internal event dbi xChange. Thus, waiting at the airport, it's a good occasion to explain how I start blogging in case it gives some ideas to people that want to start.
This is a very short post about something I though I had already blogged about.
I like SQL Monitoring active reports. The are graphical, and still very light. There is only one thing I don't like about it in 11g and it has been improved in 12c
Yesterday I was a speaker at Collaborate15 and did my presentation about reading an AWR report. That was great. Many people (and not enough seats).
Here are some aswers about questions that came later.
Great events like IOUG Collaborate is a good way to meet experts we know through blogs, twitter,etc. Yesterday evening, with nice music in the background, I was talking with Leighton Nelson about cloning PDB databases. Don't miss his session today if you are in Las Vegas. The big problem with PDB cloning is that the source must be read-only. The reason is that it works like transportable tablespaces (except that it can transport the datafiles through database link and that we transport SYSTEM as well instead of having to import metadata). There is no redo shipping/apply here, so the datafiles must be consistent.
The RAC Attack - install a RAC in your own laptop - is a great success at Las Vegas.
A frequent question about replication is the overhead in the source, because in a lot of cases the source is production. Dbvisit replicate comes with the possibility to do the minimum on the source: only the FETCHER process is there to read de redo logs and sends it to the MINE process wich can be on another server.
But maybe even that - reading those critical online redo logs - is worrying you. That's not a reason to avoid to do a PoC with the production as source. Let's see how we can use the 'archived logs only'.
There are several new features in 12c about Data Guard: cascaded standby, far sync instance. But there are also some architecture changes: new processes and new wait events.