If you are on Exadata or taking advantage of Database In-Memory it’s possible your queries will benefit for the automatically created and maintained Storage Indexes.
But what exactly are Storage Indexes and why don’t I always see a benefit from them?
Let me start by describing what Storage Indexes are in relation to Database In-Memory but remember they behavior in exactly the same way on the Exadata storage cell.
A Storage Index keeps track of minimum and maximum values for each column in an In-Memory Compression Unit (IMCU) or 1MB chunk on the Exadata storage cells. When a query specifies a WHERE clause predicate, the In-Memory Storage Index on the referenced column(s) is examined to determine if any entries with the specified value exist.
I got a great follow up question to my earlier blog on Online Statistics Gathering; that I thought might be of interest to other and worthy of a short post of its own.
The question related to sample size used to gather histograms on a table that originally had its statistics gathered via a direct path load operation.
Let’s look at any example:
Earlier this week, Oracle officially released the newest edition in the Exadata family, the Exadata SL6. The SL6 is an Exadata where the x86 database servers have been replaced by SPARC Servers. It runs the same Exadata software and Oracle Linux as the x86 version and it has the identical interfaces and APIs, so an application or end-user won’t actually know the difference.
For me the real benefit of this solution is the chance to run Oracle Database 12c on the SPARC M7 processor.
What’s so great about the SPARC M7 chip?
I’m really looking forward to the Rocky Mountain Oracle User Groups Training days next week, at the Colorado Convention Center, as it will bring several new challenges for me. I am going to be involved in three very different sessions at this year’s conference:
I was recently asked if I would ever recommend locking table statistics as a way of preventing execution plans from changing. As, with a lot questions’ regarding the Optimizer and statistics the answer was “it depends”.
There are definitely some edge cases where locking the statistics is the best approach but I wouldn’t generally recommend it to achieve plan stability. Before I share the edge cases where I believe locking statistics would help, lets first look at exactly what locking table statistics does and why it’s not a good approach to plan stability.
Anyone who knows me will tell you, my expertise is the Oracle Database and not web applications or JSON. But my new role is all about pushing myself out of my comfort zone, so I wanted to get some hands on experience with both application development and JSON in the Oracle Database.
My colleague, Mark Drake, the PM for JSON in the Oracle Database, suggested I get my feet wet by trying the new Movie Ticketing Application tutorial available on the JSON page on Oracle.com.
The Movie Ticketing Application is written in Node.js and connects to the Oracle Database via a REST Data Service. Since I recently signed up for the Oracle Database Exadata Express cloud service, I had the perfect Database setup for a web application.
A little over a year ago Connor McDonald and Chris Saxon took over answering questions posted on AskTom, which covers many topics related to building applications on top of the Oracle Database. Connor and Chris have done an amazing job of keeping up with the constant influx of questions, with nearly 16,000 answered to date.
Last week, I was lucky enough to be invited to join Connor and Chris in answering questions submitted AskTom. So, if you have any burning questions regarding the Oracle Database or building applications on top of the Oracle Database, you can submit them at AskTom and Connor, Chris or I will get back to you!
Although there have been a number of significant changes to the Oracle Database in 12c, some of my favorite new features are actually the small enhancements, designed to make your life a little easier. So, I decided to spend some time this year sharing the details on these small but extremely useful features.
One such enhancement is Online Statistics Gathering.