21. 10. 2019.

Performing stress test against Oracle database that is running in a Cloud

Today majority of enterprises are moving or at least considering moving some load into the Cloud. What you need to be aware in such case, system requirements for a Cloud load are quite different when comparing with on-premises, mainly due to many new moving parts that are not present within classical environment such as sharing […]

05. 09. 2019.

Reducing CPU consumption and Oracle licenses by fixing context switching in Oracle Db

Context switching is one of the most overlooked topics when tuning the Oracle database, as you can’t simply see it directly (e.g. “context switching” wait event doesn’t exist). Instead you should use indirect approach (through the increased CPU consumption), as it’s recorded as a CPU wait event. Context switching what it is and what impact […]

26. 02. 2019.

Impact of the JVM Garbage Collector on the realistic workload

At the last regional Java and Open Source conference where I held the presentation named: “Java Mission Control now in OpenJDK – best practice”, several questions have been raised about a way of testing JEE apps, influence of a GC (Garbage Collector) on the overall performance, new GC engines etc. With OpenJDK 11 we have […]

05. 02. 2019.

OpenJDK Mission Control – how to install it properly

If there is one tool that have almost all what is needed for monitoring, troubleshooting and tuning Java apps, that will be OpenJDK Mission Control.   There are several reasons why JMC will be hot topic in Java events from now on: More than 95% of all issues related to JVM, application servers, deployed apps […]

03. 01. 2019.

Multipath I/O and Network bonding

Event though Multipath I/O and NIC bonding is more related to sysadmin and storage admin tasks, it is good idea to grab some knowledge about those keywords as they play important role in achieving good performance. In the series of articles about disk speed I explained why it is good to know what values you […]

21. 12. 2018.

How to quickly check disk(s) speed limit on Linux – part 3

This is the third part of a series of articles about measuring performance of disk subsystem. In the first part you can find details of how to measure disk performance by using dd command: https://www.josip-pojatina.com/en/how-to-quickly-check-disks-speed-limits-on-linux/ while in the second part you can find similar information by using the hdparm utility: https://www.josip-pojatina.com/en/how-to-quickly-check-disks-speed-limit-on-linux-part-2/ In this blog I’ll […]

14. 12. 2018.

How to quickly check disk(s) speed limit on Linux – part 2

In the previous part of disk speed series you can see one way to test disk speed by using special options of the dd command. In this article another utility – hdparm will be described. What is common with the previous way of testing HDD disk performance is in it’s simplicity, meaning you only need […]

04. 12. 2018.

How to quickly check disk(s) speed limit on Linux

Many times I can testify that IT professionals are talking about performance without even try the most simplistic tests to find out what are the HW capabilities/limits they have. One of the first things I usually do when facing with unknown environment is to run several tests to find out how much I can get […]

27. 09. 2018.

Non prefixed local index and slow SQL

Recently I’ve been asked to help explain why one query is running so slow based on only SQL text and table definition that is provided. As query was pretty big (several hundreds lines of code), at the first I thought that is mission impossible, as I have no explain plan available, no running stats, no […]

16. 08. 2018.

Exadata / Linux crash – capturing kernel dump on Linux systems

This article has been motivated from real life issue experienced on Exadata system running a few dozen of Oracle databases. I have already written about Exadata shortcoming in one of previous articles where I stressed that one of the main disadvantages of Exadata machine is non-existent virtualization technology. Oracle recognizes Oracle VM as the only […]