topic Re: QlikView Server doesn't take advantage of multiple cores in QlikView

QlikView Server doesn't take advantage of multiple cores

Mon, 26 Jan 2026 18:19:17 GMT

Hello all,

Documentation states that "QlikView scales almost perfectly with the addition of more cores and more CPUs".

However, our QV11 server seems to use only one CPU (green graph in the attached image) reaching a "server timeout" response when it takes too much time, while the other CPU remains almost idle (red graph).

Could somebody give us advice about why is this happening?

Re: QlikView Server doesn't take advantage of multiple cores

Miguel_Angel_Baeyens — Mon, 29 Jul 2013 13:33:23 GMT

Hi,

Is there any chance that the chart that throws that server timeout has one or several Count DISTINCT or Aggr() functions within them? That can be the cause.

By the way, does the CPU behaves like that with any document of QlikView?

Hope that helps.

Miguel

Re: QlikView Server doesn't take advantage of multiple cores

Mon, 29 Jul 2013 16:11:41 GMT

Hola Miguel, thank you,

There are just a couple of aggr(count(distinct... used as expressions in list boxes, and some getSelectedCount(). There are also a lot of nested ifs. Do you think these could be a problem?

I'm going to check the just-one-core usage is happening with other QlikView documents.

Re: QlikView Server doesn't take advantage of multiple cores

Miguel_Angel_Baeyens — Mon, 29 Jul 2013 19:18:54 GMT

Hi,

Yes, definitely that can be one issue. Try moving those nested If() to different objects (having many with different expressions instead of one with one single big expression).

Anyway, let's see what happens to other QVW files.

Hope that helps.

Miguel

Re: QlikView Server doesn't take advantage of multiple cores

Tue, 30 Jul 2013 08:12:32 GMT

Hello,

Other QVW files use only one core too, while the other is almost idle. So I really would like to understand why and make use of the two cores (and possibly get more cores to get rid of the "server timeout").

About the nested ifs, I think it's going to be very difficult to redesign the QVW, so I would prefer to solve the core issue first.

Re: QlikView Server doesn't take advantage of multiple cores

dcheung3388 — Wed, 31 Jul 2013 10:08:44 GMT

Hi,

We are experiencing the same thing and would be a great help for any advice as well.

We have a machine with 8xquad core (32) cpu with 256MB RAM. and we tested a qvw with 5 users, and we found that we are using one CPU.

The QV process is not utilizing the server resource available.

Any suggestion would be great.

Thanks

David

Re: QlikView Server doesn't take advantage of multiple cores

Miguel_Angel_Baeyens — Thu, 01 Aug 2013 11:27:49 GMT

Hi,

If the issue is in the functions used, then there is no "core issue", because what is causing the bad performance are the expressions in the charts.

Try doing a binary load from that file to an empty one, and move some of the charts (not all of them) to see where is the issue.

Hope that helps.

Miguel

Re: QlikView Server doesn't take advantage of multiple cores

Thu, 01 Aug 2013 11:57:21 GMT

Hello,

You are right Miguel, I think the core issue wasn't there, I think I checked wrongly the task manager. To David Cheung below me: recheck your task manager, you were probably using all the cores and by mistake you thought that you weren't, just like me.

I'll check the different charts and expressions.

Re: QlikView Server doesn't take advantage of multiple cores

dcheung3388 — Thu, 01 Aug 2013 12:03:12 GMT

Hi Alzhaid, and Miguel,

We have raised this with QT, and waiting for a response on this.

We are in the midst of 'peeling the onion', layer by layer.

We have found that the Set Analysis is performing at Multi-Core CPU.

What we are now tracing is why we have a wait period before the calculation starts to perform.

This is a good exercise!...

David

Re: QlikView Server doesn't take advantage of multiple cores

dcheung3388 — Wed, 07 Aug 2013 08:55:35 GMT

Hi,

We have found the problem the cause of the problem, it's the way expression becomes a the 'single-thread' chain reaction.

Thanks for the pointer.

David

Re: QlikView Server doesn't take advantage of multiple cores

Wed, 07 Aug 2013 08:59:28 GMT

Hello David,

Could you explain further how a expression became a 'single-thread' chain reaction? (In my case I think we were using all cores in all expressions).

Re: QlikView Server doesn't take advantage of multiple cores

dcheung3388 — Wed, 07 Aug 2013 09:22:36 GMT

Hi Alzhaid,

This is what we have found and we are in the progress of conducting more test to verify the performance....

We have a qvw that is 700MB for financial reporting with 6 years of data.

Within this qvw, we have a tab with a P&L pivot table, and user can select the period they want to show, when user select a column, we noticed only 1 x CPU (32 cpu in total with 256GB RAM) was actually moving... and when we have 5 users, all the users request were queued... if the response took 30 seconds to complete, the user A would be 30 seconds, User B would then be 25-30 seconds later and continue...

If we changed the expression to a simple SUM(), all the CPU were used... so we start breaking down the expression.

We then found that within the original expression, we had a data island field called 'unit' which allows us to show the amount in "full, thousand, and million' this is a field that is selectable by the user and based on the selection, the expression would then divide on it.

We found that when trying to divide on this, it was causing (seems to be in task manager) the CPU to go into a single-thread mode.

Instead, what did was to change the expression to use a "variable" which incoroprated the expression to pickup the selected data island field.

Once this was changed, the whole expression became "multi-thread" and we could see all the CPU going crazy... And all the Users request were completed almost together...

What a learning exercise, drove a few of our us nuts... !

David