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ASM nternals: tracking down failed ASM reads

How to verify if a slave running in MySQL 5.7

Introduction Most people know that you can use SHOW SLAVE STATUS to verify if a slave is running in MySQL. Most people ...

Creating a test lab using VirtualBox / NAT networking

My job is almost completely reliant upon my ability to perform work in lab of virtual machines. Almost every action ...

ORA-10173: Dynamic sampling time-out error

Monitoring apache Cassandra metrics with Graphite and Grafana

1. Overview Despite the fact that Apache Cassandra provides a large number of metrics through the popular Metrics ...

Recursion in Hive - part 1

I am going to start this new series of blog posts talking about code migration use cases. We will talk about migration ...

MySQL InnoDB’s full text search overview

NOTE: If you want to read and play with the interactive application, it has been developed using Shiny/R in order to ...

SQL Injection with MySQL SLEEP()

Recently we've received an alert from one of our clients that running threads are high on one of their servers. Once we ...

Oracle service secrets: group and filter

At the KSCOPE16 conference in Chicago I recorded a two minute tech-tip with Bob Rhubart of OTN about adding services to ...

Things to consider when deciding on a primary key for your INNODB table

When it comes to schema design, one of the more common issues I see for INNODB tables is in the selection of a primary ...

Using Docker to visualize MySQL performance schema

Context Last week, I was pleased to present at Percona Live Amsterdam 2015 regarding the importance of Performance ...

Properly removing users in MySQL

Context Removing users in MySQL is an easy task, but there are some drawbacks to check carefully before dropping a ...

Oracle 12c - adaptive query optimization

Scenario: A user complains that a batch job that is critical for the month end business processing is taking more time ...

An effective approach to migrate dynamic thrift data to CQL, part 1

1. Introduction Recently Pythian's Cassandra team worked on one customer's request to copy data of several Cassandra ...

Licensing Oracle in a public cloud: the CPU calculation impact

Introduction: The Virtual Core Discrepancy Update 2015-May-11: Jean-Michael dug up another Amazon Web Services document ...

Exposing Innodb internals via system variables: Part 2, I/O (structure and logs)

Introduction This is part two of a five part blog series to explore InnoDB internals by looking at the related tunable ...

High "cursor: pin S wait on X" waits?

If your system meets any of the following criteria:

Exposing Innodb Internals via System Variables: Part 1, MemoryExposing Innodb Internals via System Variables

Introduction A couple of months ago I decided to give myself a refresher on the mechanics of InnoDB. Having a high ...

DECIMAL columns and a non-expected replication error

Why locking Oracle accounts is a bad idea

Time and time again I run into database accounts which are marked "LOCKED" or "EXPIRED & LOCKED". The main problem ...

ASM disk group just will not mount

I recently had an issue involving a damaged ASM disk group. Each time an attempt was made to mount the disk group it ...

Enabling large pages on Oracle Database 11g running on IBM AIX

For implementing Large Pages on AIX first you will need to choose large page size at OS level. On AIX you can have ...

How to deal with MetaData Lock

What is MetaData Lock? MySQL uses metadata locking to manage concurrent access to database objects, and to ensure data ...

More effective anti-entropy repair in Cassandra

1. Introduction Cassandra offers three different repair mechanisms to make sure data from different replicas are ...

Connection timeout parameters in MySQL

Introduction wait_timeout interactive_timeout net_read_timeout net_write_timeout What do these timeouts do in MySQL? If ...

Centralized authentication with Red Hat directory server for Linux systems

User management on Linux systems can be tedious, and when you add in more than 10 systems the chances are it is going ...

Advanced compression option caveat in Oracle 12c

Oracle 12c introduced a new capability to move a partition online, without any interruptions to DML happening at the ...

Permissions in Redshift administration

As with any database administration strategy, management of Redshift requires setting and revoking permissions. When ...