Monthly Archives: January 2014

Can you boost your Oracle database performance on HP-UX for free?

Database performance, as is true with all performance related matters, has to do with resources.

This story specifically focuses on a real life experience with Oracle database performance on HP Unix running on Intel integrity CPU’s like these:


The issue with installation is the hyper-threading aka. the use of the logical processors.
When the server is booted and is running, you can do basic performance review with a default tool like top.


In this exact case the server is running fine and there is no need to investigate further. But, in cases where there were performance issues, it would be a good idea to be aware of the numbering of the CPU’s in this overview (0, 2). This numbering suggests there would also be a ‘1’ and, where there would be a ‘1’ there would probably also be a ‘2’…

Yes there is and it is called ‘lcpu_attr’. A HP Unix kernel parameter which is, to my taste, a bit odd, not well known or well documented…

lcpu_attr (Tunable Kernel Parameter)

When turned on, lcpu_attr activates the logical CPU’s immediately. When you run top again, this is what it’ll look like (immediately)


Okay! Great… but… there are some catches.
This parameter lcpu_attr is a dynamically tunable kernel parameter but… it’ll crash your databases. So you will need a minimum of planned downtime for this action.

Also, you can set hyper-threading on in the EFI boot-loader.
But then you should be aware of this!

In the end, in this real-life story, we helped the situation advance by just doing:

1. stopping Oracle database(s)
2. kctune lcpu_attr=1
3. starting Oracle databas(s)

All in all, it could be not difficult to boost your Oracle database performance on HP-UX for free!

Thanks to my good friend Gerard van der Kooij for finding the final link!