topic Re: cache warmer? in QlikView

cache warmer?

Mon, 26 Jan 2026 18:19:17 GMT

Happy M-day, everyone in the USA.

So, I've notice one bit of thing that is helping the slow browsing issue. When I open my dashboard from the browser, for the first time, it is slow. using a different browser, later, turn out to be faster.

It reminds me of the MS product that, they have a way to load the data to be browse into memory. Someone call that technique a cache warming; liked the data is cached and all warm-up ready to go.

is there anything liked that for QV11?

I have a App server, web server, and a Dist server, then clients.

Re: cache warmer?

Vincenzo_Esposito — Mon, 30 May 2016 16:41:44 GMT

I don't know if it's your case. But when I experience performance issue just in one browser the cause is very likely related to some debug tool still active (such as firebug or chrome inspector) JavaScript debugging is an heavy process which result in poor performance.

Re: cache warmer?

Mon, 30 May 2016 16:48:50 GMT

good guess.

It is slow with IE and debug isn't running.

Re: cache warmer?

Clever_Anjos — Mon, 30 May 2016 16:50:12 GMT

Are you using the "pre load" option at QMC? It enables QVS to load your qvw once it reloaded

Re: cache warmer?

swuehl — Mon, 30 May 2016 16:54:24 GMT

You probably noticed the effect of the aggregation cache in QV server.

This should be independent from the browser, so even when you are using the same browser and repeating selections, you should notice that the second time you do a selection, the results of the aggregations / expressions are shown much faster, that's because QV is indeed using a cache to store calculation results.

The QlikView Cache

Re: cache warmer?

swuehl — Mon, 30 May 2016 16:57:38 GMT

And something like this probably comes closest to your idea of a 'cache warmer':

Power Up your Big Apps with Binary Index Expansion • Blog • AfterSync

Re: cache warmer?

alexdataiq — Mon, 30 May 2016 17:27:58 GMT

Hi Clever,

Haven't heard of this "pre load" option in QMC, is it something new? Where do I find it?

Regards

Re: cache warmer?

Clever_Anjos — Mon, 30 May 2016 17:31:37 GMT

This feature will load your qvw into memory, but not pre aggregate and calculate any object

Re: cache warmer?

alexdataiq — Mon, 30 May 2016 17:41:53 GMT

Thanks, I guess I've never seen that feature before in the QMC. Does the preload works instantly after a reload?

Cheers

Re: cache warmer?

swuehl — Mon, 30 May 2016 17:42:06 GMT

You can also find a lot of useful information about caching / RAM occupation and how the server handles new / inactive document sessions in this post and the referenced documents / white papers;

Re: RAM Usage in QlikviewServer

Re: cache warmer?

Clever_Anjos — Mon, 30 May 2016 17:43:29 GMT

"instantly " = a few seconds, yes

Re: cache warmer?

Mon, 30 May 2016 17:50:46 GMT

good point.

pre load- check

manually reload - check.

slow.

Re: cache warmer?

Mon, 30 May 2016 17:53:30 GMT

Thank you, swuehl !

A lot of good reads.

Re: cache warmer?

Peter_Cammaert — Mon, 30 May 2016 18:02:12 GMT

If I read your post correctly, you may be experiencing the simple load of a document in memory by QVS. The very frist user that opens a document will cause the QVS to load the document in memory. That in itself will account for a delay from a few seconds to many minutes, depending on the size of your document. The solution to this, as explained by the others, is the pre-load option which causes the QVS to load a document in memory immediately after a restart and whenever a document is reloaded. Even when no-one really needs or uses that document at that moment.

This is especially useful for the larger documents, as nobody likes to wait a quarter of an hour or more for those hundreds of gigs to load. And especially not when you can be sure that after a period of disuse, these documents may get kicked out of server RAM again.

After loading the document in memory (no cache) various calculations and aggregations wil create subsets of data that will be cached for real. Reading the same dataset and esxpression results from the cache instead of having to recalculate will speed up selections and object filling.

All of this impacts both RAM usage and response speed.

Best,

Peter

Re: cache warmer?

alexdataiq — Mon, 30 May 2016 18:11:05 GMT

So, does the preload option indeed helps to seed the cache of document?

Cheers

Re: cache warmer?

oknotsen — Mon, 30 May 2016 18:11:14 GMT

"slow"? What slow, who slow, why slow? You might want to be a little bit more descriptive .

Re: cache warmer?

Peter_Cammaert — Mon, 30 May 2016 18:13:35 GMT

AFAIK no. Pre-load doesn't simulate users, It just loads the document in RAM before anyone uses it.

Re: cache warmer?

oknotsen — Mon, 30 May 2016 18:13:58 GMT

The document has no cache; the server does.

Preload only loads the document in memory. This can already be a time saver for the first person to use the document each day as huge documents can take some time.

Calculations in cache is only stored if actual selections are made. What you can do is "cache pre-heating" by for example run a "test script" that makes common selections after the document is reloaded.

Re: cache warmer?

Mon, 30 May 2016 18:14:57 GMT

may be it is fast for some apps. the app, i've adopted here, isn't getting noticeable speed.

Re: cache warmer?

oknotsen — Mon, 30 May 2016 18:19:56 GMT

Preload will only be noticable for documents of some size.

I had a customer with 2 billion rows of data in his apps. The difference was from 5+ minutes to just seconds.