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February 2016

AskTom–some thoughts on the future

The structure of an AskTom question contains four elements:

  • The original question
  • Our answer
  • A review, which can be posted by anyone
  • And then we can opt to add a single Followup to any of those reviews

 

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We’re thinking of changing AskTom to allow greater flexibility, namely:

EM13c Upgrade Tips- Part II

There is a flurry of excitement about Enterprise Manager 13c and I’m blown away by how many customers are looking not just to install and test out the new release, but have plans already underway to upgrade to it.

Video: Amazon Web Services (AWS) : Relational Database Services (RDS) for MySQL

Here’s another video on my YouTube channel. This one is a quick run through of RDS for MySQL, a DBaaS offering from Amazon Web Services.

The video was based on this article.

If you watch the little outtake at the end you will hear me cracking up with the goofiest while filming Brian ‘Bex’ Huff‘s clip. :)

Cheers

Tim…

Bitwise operations

The long existing BITAND function is now within the documentation, to let you do logical AND on two numbers, and is also available from PL/SQL

image

 

If you need other bit operations, a little boolean math should suffice Smile Just make sure you stay within the limits of BINARY_INTEGER


CREATE OR replace FUNCTION bitor( x IN binary_integer, y IN binary_integer ) RETURN binary_integer  AS
BE

Annoying your user base never pays off!

lego-face-angryThis post is heavily inspired by the events of #RIPTwitter and the recent Fine Brothers fiasco, but it could apply to just about any company, product or person. When I say user base, I could easily mean customers or fan base.

Big Nodes, Concurrent Parallel Execution And High System/Kernel Time

The following is probably only relevant for customers that run Oracle on big servers with lots of cores in single instance mode (this specific problem here doesn't reproduce in a RAC environment, see below for an explanation why), like one of my clients that makes use of the Exadata Xn-8 servers, for example a X4-8 with 120 cores / 240 CPUs per node (but also reproduced on older and smaller boxes with 64 cores / 128 CPUs per node).

The Oracle wait interface granularity of measurement

The intention of this blogpost is to show the Oracle wait time granularity and the Oracle database time measurement granularity. One of the reasons for doing this, is the Oracle database switched from using the function gettimeofday() up to version 11.2 to clock_gettime() to measure time.

This switch is understandable, as gettimeofday() is a best guess of the kernel of the wall clock time, while clock_gettime(CLOCK_MONOTONIC,…) is an monotonic increasing timer, which means it is more precise and does not have the option to drift backward, which gettimeofday() can do in certain circumstances, like time adjustments via NTP.

The first thing I wanted to proof, is the switch of the gettimeofday() call to the clock_gettime() call. This turned out not to be as simple as I thought.

No Data Loss without Sync Data Guard

A few months ago I wrote about an exciting product that allows you to achieve no data loss in a disaster even without using the maximum protection Data Guard that relies on super expensive synchronous networks. Recently I had a chance to actually work on that system and replicate the scenarios. Here I explain how that actually works, with commands and actual outputs.

Background

First, you may want to refresh your memory on the concept of that product in the earlier blog http://arup.blogspot.com/2015/04/no-data-loss-without-synchronous-network.htmlThe product is Phoenix system from Axxana.

Friday Philosophy – Database Performance is In My Jeans

Database performance is in my jeans. Not my genes, I really do mean my jeans – an old pair of denim trousers. I look at my tatty attire keeping my legs warm and it reminds me of Oracle database performance.

comfortable, baggy, old, DW jeans

comfortable, baggy, old, DW jeans

Parallel DML

A recent posting on OTN presented a performance anomaly when comparing a parallel “insert /*+ append */” with a parallel “create table as select”.  The CTAS statement took about 4 minutes, the insert about 45 minutes. Since the process of getting the data into the data blocks would be the same in both cases something was clearly not working properly. Following Occam’s razor, the first check had to be the execution plans – when two statements that “ought” to do the same amount of work take very different times it’s probably something to do with the execution plans – so here are the two statements with their plans:

First the insert, which took 45 minutes: