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 operational team.
Besides this blog, I participate in the Oracle Community in forums, blogs, articles and presentation.
All that is referenced from my twitter account:
A question that I had several times: in Enterprise Manager, in the screen about one SQL statement, the 'statistics' tab shows the number of executions, elapsed time, etc. Question is: which time window does it cover? There is a one hour chart above, and two timestamps displayed as 'First Load Time' and 'Last load Time', and we don't know which one is related with the execution statistics numbers. I'll explain it clearly on an example.
Do you know why Oracle Database is a leader in the database market since 30 years? Do you know any other software that is still the leading solution after decades? It think that it is because Oracle has been a good software from the get-go. Many early decisions in the software architecture have revealed themselves later to be the right decision. Several decisions, such as the C language that made it portable to all platforms that were relevant during those 30 years, or the parallel server that has brought RAC when standalone servers were not able to scale anymore. Here, I will illustrate a decision made 15 years ago that has made the whole 12c pluggable databases stuff possible.
When can we use IOT? That's a question I had when giving recently the Oracle DBA essentials workshop. the DBA Essential is very dense and there is only half a day about performance. We have the Oracle Performance Tuning workshop to go into those details. But IOTs are under used in my opinion, so I'll post a use case for them where they are a good idea.
System statistics can be gathered in NOWORKLOAD or WORKLOAD mode. Different values will be set depending on that and the others will be calculated - derived from them. We can see defined values from SYS.AUX_STATS$ but here is a script that shows the calculated ones as well.
At Oracle Open World 2014, or rather the Oaktable World, Chris Antognini has presented 'Indexes: Structure, Splits and Free Space Management Internals'. It's not something new, but it's still something that is not always well understood: how index space is managed, block splits, fragmentation, coalesce and rebuilds. Kyle Hailey has made a video of it available here.
For me, it is the occasion to share the script I use to see if an index is fragmented or not.
Oracle's OpenWorld has ended. It was the fist time I attended this great event and it really is a "great" event:
- 60000 attendees from 145 countries
- 500 partners or customers in the exhibit hall
- 400 demos in the DEMOgrounds
- 2500 sessions
This is the session I preferred at Oracle Open World. Well, I'm writing that before going to @ludodba one and I'm sure I'll have then two preferred sessions... So Vit Spinka has presented the internals of the new multitenant architecture. It's always good to play with some internals things. Not only for the geeky fun of it but also because it helps understand how it work and address issues later.
I'm currently following the session 'Real-World Performance of Star and Snowflake Schemas' with Michael Hallas, Andrew Holdsworth, John Clarke. It's really a good presentation. the Real Performance team tries to spread messages about how to design for performance. But today I'll not blog about what I've seen but about what I've not seen. Everybody talks about those nice 12c features that are useful in BI workloads, such as adaptive joins, adaptive parallel distribution, vector 'in-memory' aggregation, etc. Nobody talks about Adaptive Bitmap Pruning.