Search

Top 60 Oracle Blogs

Recent comments

19c

Video : Vagrant Oracle Real Application Clusters (RAC) Build

In today’s video we’ll discuss how to build a 2-node RAC setup using Vagrant.

This video is based on the OL8 19c RAC build, but it’s similar to that of the OL7 19c RAC build also. If you don’t have access to the patches from MOS, stick with the OL7 build, as it will work with the 19.3 base release. The GitHub repos are listed here.

If you need some more words to read, you can find descriptions of the builds here, as well as a beginners guide to Vagrant.

Oracle 19c Automatic Indexing: Indexing Partitioned Tables Part I (Conversation Piece)

In this little series, I’m going to discuss how Automatic Indexing works in relation to Partitioning. I’ve discussed Indexing and Partitioning many times previously and how Oracle has various options when indexing a partitioned table: Non-Partitioned Index Globally Partitioned Index Locally Partitioned Index So the question(s) are how does Automatic Indexing handle scenarios with partitioned […]

Oracle 19c Automatic Indexing: Indexing With Stale Statistics Part III (Do Anything You Say)

In Part I of this series, we saw how Automatic Indexing will not create a viable Automatic Index if there are stale or missing statistics on the underlining segments. In Part II we saw how these SQL statements effectively become blacklisted and when segment statistics are subsequently collected, Automatic Indexing will still not create viable […]

Oracle 19c Automatic Indexing: Indexing With Stale Statistics Part II (Survive)

    In my previous post, I discussed how having stale statistics, usually a bad idea, is especially problematic with regard Automatic Indexes as it usually results in viable automatic indexes only being created in an UNUSABLE/INVISIBLE state. If we were to now to collect the missing statistics:   If we now repeatedly re-run the […]

Oracle 19c Automatic Indexing: Indexing With Stale Statistics Part I (Dead Against It)

A “golden rule” when working with Automatic Indexing is that things don’t work properly if there are stale statistics on the dependant objects. Stale statistics can of course be problematic but they can be particularly troublesome when dealing with Automatic Indexing. In the Oracle Autonomous Database environments, this issue is addressed somewhat by the new […]

Compression default settings

If you are loading a data warehouse or similar environment where your default approach would probably be to compress all objects because they are predominantly read only, you do not need to head back into your DDL scripts and add a “COMPRESS” clause to every table.

You can set the default compression level at the tablespace level. Here’s an example of that in action

Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part II (Sound And Vision)

  In my previous post, I discussed how the Automatic Indexing task by using Dynamic Sampling Level=11 can correctly determine the correct query cardinality estimates and assume the CBO will likewise determine the correct cardinality estimate and NOT use an index if it would cause performance to regress. However, if other database sessions DON’T use […]

Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part I (The Prettiest Star))

In my previous few blog posts, I’ve been discussing some issues in relation to how Automatic Indexes handle SQL statements that accesses skewed data. In this post, I’m going to setup the scenario in which Automatic Indexing can potentially use Baselines to help address some of these issues. BUT, as we’ll see, I’m having to […]

Oracle 19c Automatic Indexing: CBO Incorrectly Using Auto Indexes Part II ( Sleepwalk)

As I discussed in Part I of this series, problems and inconsistencies can appear between what the Automatic Indexing processing thinks will happen with newly created Automatic Indexing and what actually happens in other database sessions. This is because the Automatic Indexing process session uses a much higher degree of Dynamic Sampling (Level=11) than other […]

Oracle 19c Automatic Indexing: CBO Incorrectly Using Auto Indexes Part I (Neighborhood Threat)

Following on from my previous few posts on “data skew”, I’m now going to look at it from a slightly different perspective, where there is an inherent relationship between columns. The CBO has difficulties in recognising (by default) that some combinations of column values are far more common than other combinations, resulting in incorrect cardinality […]