19. 02. 2019.

Bulk collect and memory limits

We all know that for bulk collect PL/SQL operation it’s important to keep the memory consumption under control. For that reason all bulk collect operations should be combined with a LIMIT clause like in the following code fragment: Setting the limit to process only 10K records in bulk is does not impress me in a […]

11. 02. 2019.

Performance comparison: Python & cx_Oracle versus SQL*Plus & SQL*Net

In this article I want to check the truth about the slowness of Python language when it comes to retrieving data directly from Oracle database. Second goal is to show graphically impact of changing the array size on performance, which is not possible and convenient to do with SQL*Plus.   Python is widely used as […]

10. 02. 2019.

Impact of the parameter arraysize on performance

Main goal of this article is to explain impact of the parameter arraysize on database performance. First it’s important to define what array size is. The array size is the number of rows fetched by the server. I’m using Oracle’s SH demo schema, and it’s SALES table which has almost 1 million rows. In the […]

04. 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 […]

18. 10. 2018.

Undo impact on Oracle Db performance

Many times I’ve been hearing how REDO is the most important to tune in order to have database running fast, but very rare I can hear that someone is mention UNDO as another piece of puzzle that is also extremely important to keep in good shape. In this article I’ll try to avoid what you […]

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 […]

13. 09. 2018.

Bash performance tuning by example – How to delete 1 million files from file system, and how to do that fast?

In this article I’ll show my approach to solve real world performance problem by using bash scripting language.   Problem statement is: How to delete 1 million files from file system, and how to do that fast?   File system maintenance is important aspect of sysadmin job. It’s not only important to maintain file system, […]