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 […]

19. 11. 2018.

LOB data type side effect on DML trigger based auditing

I’ve been listening scary stories about all kind of issues related to LOB data types (there are many data types based on the LOB concept like Spatial, CLOB, BLOB, XML…). In this article I’ll put some light on one of the lesser known consequences related to mechanism how LOB works under the hood. To solve […]

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 […]

06. 09. 2018.

Performance tuning by using optimistic instead of pessimistic locking – Part 2

In the previous blog I described how to implement optimistic locking logic by using ORA_HASH function call. Here I’ll explore another option that I frequently use – last time when the row has been changed. Let’s create test table by using DEPT table as a base with one additional column – MOD_TIME. For MOD_TIME column […]

24. 08. 2018.

Performance tuning by using optimistic instead of pessimistic locking

Even though Oracle Db started with optimistic locking many years back, old fashion programming style can still be observed too often. In this article I’ll explain why you should avoid using pessimistic locking as mach as possible, and will show one of the alternative way to do the same task by using optimistic locking. I’ll […]

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 […]

28. 07. 2018.

Supplemental logging – when to use it (and when not)

Supplemental logging feature along with streaming and CDC (change data capture) is available for a long time and is used mainly as one of the integration options especially for loading data from transactional (OLTP) into DW (Data Warehouse) staging tables. During my engagement on project for one large retailer, I noticed significant performance penalties due […]