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October 2018

Partial Indexes–Take Care With Truncate

Partial indexes are a very cool feature that came along with Oracle 12c. The capability at partition level to control index existence allows for a couple of obvious use cases:

1) You index the data in recent partitions only, because small amounts of data are aggressively searched by applications and/or users, but not the older data because the queries for older data are either less frequent or are more analytical in nature.

Using Microsoft Flows to Automate RSS Feeds

Now everyone knows how I like to automate everything and for those that have known me since I started sharing content, I pretty much cried a thousand tears when the personalized news source, Prism disappeared.

I’ve been working with RSS feeds aggregators to send me content each day to read, but I get frustrated with having to go find them sent to my spam folder or not being able to get to the links, so I wanted to try something new.

ODBV3 and ASM

At Trivadis Performance Days 2018 (awesome event by the way) I promised to deliver ODBV3 with support for ASM – and here it is! </p />
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Understanding Distribution in #Exasol

Exasol doesn’t need much administration but getting distribution right matters

Exasol uses a clustered shared-nothing architecture with many sophisticated internal mechanisms to deliver outstanding performance without requiring much administration. Getting the distribution of rows between cluster nodes right is one of the few critical tasks left, though. To explain this, let’s say we have two tables t1 and t2:

“Hidden” Efficiencies of Non-Partitioned Indexes on Partitioned Tables Part I (The Jean Genie)

When it comes to indexing a partitioned table, many automatically opt for Local Indexes, as it’s often assumed they’re simply easier to manage and more efficient than a corresponding Global Index. Having smaller index structures that are aligned to how the table is partitioned certainly has various advantages. The focus in this little series is on […]

Ansible tips’n’tricks: a different output option

When running ansible scripts, occasionally you wonder why a given task has failed. I found out more than once that it’s commonly a problem with the script, not the engine ;) Finding out exactly where in the script I made the mistake can be more of a challenge.

With the default ansible settings, output can be a bit hard to read. Consider this example: I do quite a bit of patching in my lab, and this almost always requires an upgrade of OPatch (d’oh!). So instead of connecting to each of my hosts and performing the same unzip command over and over again, I thought of using something else. Why not use ansible for this task? It won’t get tired copying/unzipping OPatch to all the destinations I indicate in my configuration. And it won’t introduce a mistake when dealing with the fifth ORACLE_HOME on the third server…

Join Cardinality

Following up my “Hacking for Skew” article from a couple of days ago, Chinar Aliyev has written an article about a method for persuading the optimizer to calculate the correct cardinality estimate without using any undocumented, or otherwise dubious, mechanisms.

Easy as pi…. hole.

A slight digression from my normal database-focussed content today Smile

In internet bandwidth and latency strapped Perth (Western Australia), every last drop of internet counts. Recently I stumbled upon this blog post by Troy Hunt about using a Raspberry Pi to serve as a local DNS to filter out unnecessary content. Personally, I don’t care about the content as such (I don’t like ads, but I do acknowledge that they are generally a necessary “evil”), but for me it is about getting the most performance out of my lowly internet connection until the technology evolves in Australia.

Repairing a Linux host with disk/filesystem issues

This is a writeup on some scenario’s for disk issues that you could encounter when running linux systems. The linux systems I am talking about are centos/redhat/oracle (EL) version 7 systems. This is just a writeup for myself to know how to deal with different scenario’s, hopefully other people find this interesting too. I don’t believe there is any difference for the below scenario’s and resolutions between running physical/bare metal, virtualised or in the cloud, provided you can get access the you need (like the BIOS POST console). The test configuration uses (legacy) MBR (meaning non UEFI), grub2 as boot loader, LVM for meta devices (you don’t want to run without LVM!!) and XFS for the filesystems.

Unindexed Foreign Keys in Oracle and PostgreSQL

A new blog post on the Databases at CERN blog: verifying (with pgSentinel) that PostgreSQL does not lock full tables like Oracle does when the foreign key is not indexed.

https://db-blog.web.cern.ch/blog/franck-pachot/2018-09-unindexed-foreign-keys-oracle-and-postgresql

Unindexed Foreign Keys in Oracle and PostgreSQL