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January 2017

Do, or do not. There is no "try".

About 7 months ago, I was reading an article about some of the new features that were in javascript/ecma/coffeescript or whatever it is called now. One of the things that stuck out, was promises. I liked the idea of "asynchronous" execution with a possible chained dependency, that you could just define and run, and then carry on with other tasks without having to wait for the result. What you do instead, is you receive a "promise" of the execution. A promise that at some point will contain the result from your call.

The Oracle database has the capability to do this already in dbms_scheduler using chains, but it is not dynamic and the complete flow has to be defined up front.

Trusted Information Sharing – ABAC Architecture

In my previous post, I introduced you to the two concepts of Role-Based Access Control (RBAC) and Attribute-Based Access Control (ABAC). ABAC resolves a number of the limitations associated with RBAC, as I discussed in that post. In this post, I wanted to drill into the architecture underlying ABAC a little bit more.

In simple terms, there are four main parts of the ABAC architecture. These are:

jmeter – getting started

jmeter

This blog post is just a start at documenting some of my experiences with jmeter. As far as load testing tools go, jmeter looks the most promising to me. It has an active community, supports many different databases and looks quite flexible as far as architecting different work loads goes.

The flexibility of jmeter also makes it hard to use. One can use jmeter for many other things besides databases so the initial set up is a bit oblique and there look to be many paths to similar results. As such, my understand and method for doing things will probably change considerably as I start to use jmeter more and more.

I’m installing it on a mac and using RDS instances.

installing jmeter

Real-Time Materialized Views in #Oracle 12c

helpshttps://uhesse.files.wordpress.com/2015/10/helps.png?w=600&h=558 600w, https://uh

How to move Partitions ONLINE and make them READ ONLY in #Oracle 12c

readonlyhttps://uhesse.files.wordpress.com/2017/01/readonly.png?w=574&h=60

What you "liked" last year…

Well…when I say “liked”, what I mean is “the stuff you all clicked on a lot” last year. Whether you liked it or not will remain one of those great mysteries Smile

The top 6 posts from 2016 were:

https://connormcdonald.wordpress.com/2015/11/25/ora-14758-last-partition-cannot-be-dropped/

https://connormcdonald.wordpress.com/2013/01/20/exchange-partition-those-pesky-columns/

2016 DBAKevlar Year in Review

How was 2016 for me?

Graphics for SQL Optimization

Dan Tow, in his book SQL Tuning, lays out a simple method of tuning SQL queries. The method is

  • Draw a diagram of each table in the query with Children above Parents
  • Draw join lines between each join (many-to-many, one-to-many)
  • Mark each table with a predicate filter and calculate the amount of table filtered out

Then to find a great optimal optimization path candidate

  1. Start at the table with the strongest predicate filter (the filter that returns the fewest % of the table)
  2. join down to children (if multiple children join to child with strongest predicate filter)
  3. If you can’t join to children, join up to parent

The basics are pretty simple and powerful. Of course there are many cases that get more complex and Dan goes into these complex cases in his book.

Hot cloning and refreshing PDBs in #Oracle 12cR2

Hot cloning PDBs is new in 12.2, so you don’t have to put the source PDB into READ ONLY mode before the cloning if you have it in local undo mode. I suppose shared undo mode will become very unpopular. Another 12.2 New Feature is the option to clone a PDB that can be refreshed from the source PDB. I will show both features with this article, but you may of course do hot cloning without a later refresh. In this case, just leave out the REFRESH MANUAL clause and you don’t have to OPEN READ ONLY the cloned PDB afterwards. On a high level, what I demonstrate is this:

Oracle Database Cloud (DBaaS) Performance - Part 1 - CPU

After having looked at the performance consistency provided by the Oracle Database Cloud offering in the previous series, I'll focus here on the raw performance figures I've measured during my tests, starting with the CPU related performance findings.

One of the first surprises is related to the fact that Oracle uses a unit called "OCPU" to specify the CPU capacity provided, which is explained here: