Finding the shortest path from Country A to Country B – using Neo4J and Node

Graph Databases are good at recording nodes and edges – and even more at performing queries that traverse the edges. Some challenges can be dealt with in Graph Databases far more elegantly and efficiently than for example in relational databases using traditional SQL.

As simple example, this article will create a Neo4J Graph Database instance, populated with the countries of the world (the nodes) and the (land) borders between the countries (the edges). The country (more...)

dbca doesn’t list diskgroups

This is an Exadata machine running GI version 18.3.0.0.180717 and DB version 12.1.0.2.180717. On one of the DB nodes while running dbca, it doesn’t list the diskgroups. it works fine on the other node.

I cheked the dbca trace and found that the kfod command was failing. I tried to run it manually and got the same error:

[oracle@exadb01 ~]$ /u01/app/18.0.0.0/grid/bin/kfod op=groups verbose=true
KFOD-00300:  (more...)

Querying the amount of redo in Oracle Database

When a database starts to churn more redo then normal, it is handy to be able to extract the amount of redo over time, to be able to plot this in a graph.  The below allows you to extract this info 🙂

Query for redo generation

Query to obtain the amount of redo generation over time by hour and MB:

set pages 999 lines 400
select to_char(trunc(first_time, 'HH24'), 'DD/MM/YYYY HH24:MI:SS') date_by_hour, sum(round(blocks*block_size/1024/1024)) CHURN_IN_MB
from v$archived_log
 (more...)

Building a Conference Session Recommendation engine using Neo4J Graph Database

This article describes a use case for which a traditional SQL-powered relational database approach can provide a solution – but for which that traditional approach is not the optimal solution. SQL is jack of all trades – you can make it do almost anything you need. And therefore it is easy to become your hammer and every challenge a nail. This article is if anything meant to open my and maybe your eyes to the (more...)

CQRS through Twitter – more fun than meaning

As part of my 50 Shades of Data presentation, I talk about CQRS – Command Query Responsibility Segregation. The idea that you can have one or more read only data stores with data replicated from the master store where all data manipulation (commands) take place. In a different presentation, I introduce Apache Kafka and explain its concepts. In this article, these two topics come together, in a light hearted fashion.

My starting point is the (more...)

Querying connected data in Graph databases with Neo4j

TL;DR;

· Graph databases are ideal for query use cases with data with complex relationships and layers of connections

· Its query language is fast, efficient and allows for retrieval of information at deeper levels of abstraction in the data

· Neo4j is currently the most popular Graph database, and its declarative query language is Cypher

· Concepts in Cypher are “nodes”, “relationships”, and “properties” for storing the data

· Keep queries small and simple (more...)

Column And Table Redefinition With Minimal Locking

TLDR: Note to future self… (1) Read this before you modify a table on a live PostgreSQL database. If you do it wrong then your app might totally hang. There is a right way to do it which avoids that. (2) Especially remember the lock_timeout step. Many blog posts around the ‘net are missing this and it’s very important.

Yesterday I was talking to some PostgreSQL users (who, BTW, were doing rather large-scale cool stuff (more...)

Pass Summit 2018 Keynote 11/7

So I made it to PASS Summit 2018.  After a flight from an airport with one gate-  yes, you heard me right, one gate.  No Wi-Fi, no connectivity and four employees at the airport.  It was a new level of disconnect.

After a number of parties last night, I’m at the bloggers table for the first keynote this morning.  The first keynote started with an energized talk from PASS president and (more...)

Oracle Database EM 18 XE Available to Remote Clients

I found lot of posts about Oracle Database 18 XE. It's very interesting for me.  I didn't blog about how to install, because it's very easy for using rpm package and document very helpful.
I was interested in Enterprise Manager Database Express 18.4.0.0.0. How it looks like?
- Installing. I used CentOS7.
[student@centos-learning ~]$ sudo yum -y localinstall oracle-database*18c*
[student@centos-learning ~]$ sudo rpm -qa |grep oracle
oracle-database-preinstall-18c-1.0-1.el7.x86_64
oracle-database-xe-18c-1. (more...)

Exploring Autonomous Databases – Client Credentials

The wallet zip file from ATP or ADW includes the connection information for all the ATP and ADW databases you have created under the cloud account, even though the credential zip file name is "wallet_.zip".

List of Bank Holidays For England in SQL Format

First off, create a table to store the bank holiday values. You may need to adjust this slightly depending on your SQL server technology being used (this was tested on MySQL Server).  [crayon-5bb4e0b3b1755979540269/] Insert the bank holiday values below. This table is currently for 2012 up to 2019 for England and Wales.  [crayon-5bb4e0b3b175d512369946/] For a

Recreate Database Using Only Datafile and Logfile

Let’s have look on the steps are used by Oracle DBA  for “Recreate Database Using Only Datafile and Logfile”.
Backup of the control file in trace

SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE;

create password file and service

D:\> orapwd file=D:\oracle\product\10.2.0\db_1\database\PWDdba71.ora password=sys entries=10

D:\> oradim -new -sid dba71 -intpwd sys -maxusers 10 -startmode auto -pfile D:\oracle\product\10.2.0\admin\dba71\pfile\init.ora

set the environment and start the database in nomount

D:\>set oracle_home=D:\oracle\product\10.2.0\db_1
 (more...)

Create Oracle Database 18c on Windows – Advanced Configuration for the pros

If you are setting up a production system or similar, you will need to go through the advanced configuration. The best option is to choose "Set Up Software Only" in Oracle Universal Installer (OUI) to complete the Oracle software installation, then use Database Configuration Assistant (DBCA) to create a new database. OUI and DBCA have the advanced configuration. The OUI advanced configuration is not "advanced" enough, DBCA lets you customize the database configuration options - (more...)

Create Oracle Database 18c in 3 clicks!

After the Oracle Database 18c software install, the database creation is only 3 clicks using the Database Configuration Assistant! The Oracle defaults are OK!

MySQL 8: New Features

After installing mysql 8 on my ubuntu i did a lookaround for the new features. Oracle itself stated:

This is really cool, but how to test this?
A first look inside the standard data directory /var/lib/mysql shows:
/var/lib/mysql# ls -l
insgesamt 168012
-rw-r----- 1 mysql mysql       56 Aug 17 20:53 auto.cnf
-rw-r----- 1 mysql mysql      498 Aug 17 20:53 binlog.000001
-rw-r----- 1 mysql mysql      554 Aug 17 21:07 binlog.000002
-rw-r----- 1 (more...)

mysql 8: installation on ubuntu

Today i tried to install mysql 8 on my ubuntu:
First i visited the site https://dev.mysql.com/downloads/repo/apt/ which says:
So i downloaded this file (https://dev.mysql.com/get/mysql-apt-config_0.8.10-1_all.deb) and here we go:

# dpkg -i mysql-apt-config_0.8.10-1_all.deb 

Vormals nicht ausgewähltes Paket mysql-apt-config wird gewählt.

(Lese Datenbank ... 414911 Dateien und Verzeichnisse sind derzeit installiert.)

Vorbereitung zum Entpacken von mysql-apt-config_0.8.10-1_all.deb ...

Entpacken von mysql-apt-config (0.8.10-1) ...

(more...)

Where to find the oracle-database-ee-18c-1.0-1.x86_64.rpm package?

After writing about the release of Oracle database 18c i wanted to download
oracle-database-ee-18c-1.0-1.x86_64.rpm
to try the rpm-based installation.
But this rpm is not included in
LINUX.X64_180000_db_home.zip
The oracle documentation shows:
 But on OTN and Delivery Cloud only the zipfile without the rpm can be downloaded...

So let's see, when the download pages are updated...

Oracle 18c database is released for Linux (on premise)

After my posting nearly a week ago about the published 18c documentation on monday the binaries for Oracle 18c database were released:


and

 Here the link to the download page: oracle.com

In one of the next postings i will try a rpm installation...

Session using a database link hangs on “SQL*Net more data from dblink”

I have a client who recently move a database server from on-premise to a Cloud provider.  A database on this database server had a database link to their E-business database in the Oracle Cloud.  Since the move, any sessions in the database that use the database link to the E-business database would hang if the query was to return large dataset.

Below is selecting from dual over the database link that worked:

SQL>  (more...)

Index Monitoring in Oracle Database

Applies to ONLY Oracle Database 10gR1 through to 12cR1.
In Oracle Database 12cR2, this feature is replaced.  A new blog post of this feature will be posted in due course.

Since Oracle 10g, you can monitor indexes to see if they are being used or not.  Which is very useful as indexes, consume unnecessary CPU and I/O on DML activity if not used.  Therefore, it’s recommended to monitor indexes and any unused (more...)