Preload behaviour understanding

[Aditya_Chitale]

Hello community,

As the heading says, I want to understand how the preload in Qlik Sense works. I have gone through the Qlik Help page but found very less information on this topic. The thing is, I am applying preload to an app of size 40gb. Without preload the app takes almost 20 min to open and load charts. after preload, it opens in about 1-2 mins which is great.

But the problem is, we have huge number of such big apps. some reaching upto 90-95 gb. When we preload multiple such apps, the server memory reaches its threshold and the preload looses its purpose as the apps become slow to open again.

The scenario that I was testing is, if I keep the preload holded in memory for 12 hours, the apps apps will be quick to open for the mentioned preload period, this also means (as per my understanding) that if I reduce the preload hold time from 12 hours to 30 mins, the apps will open quickly only after and within 30 mins the preload completes. But in actual, even if I change the preload hold time to 30 min, and access the app after 30 min, the app opens quickly (need understanding on this. why does this happen ?).

Further on doing some research, I also came to know, that if any user opens the app on his machine, and even if the preload expires, the app will still open comparatively quickly for other users. But in my case there are no users that could open the app so what could the the reason for quick opening of apps even after the preload expires ?

Please note that I am reducing the preload hold time to reduce load on server resources.

Regards,

Aditya

[marcus_sommer]

AFAIK there is no mechanism in Qlik to clear the RAM else the parts are flagged either as reserved or as free - depending on various configurations, mostly timeouts. If there is a new request the as free flagged parts are used by overwriting the outdated stuff respectively put in a queue if not enough resources are available.

Beside the preload-settings you may need to adjust other settings, too - for example user-sessions related ones.

[Aditya_Chitale]

@marcus_sommer , but if you say there is no mechanism in Qlik to clear the RAM, then what role does the preload timeout play ? Here I have specified time in minutes till which the preload will remain hold in memory.

As for other setting like user session timeout, we have set it to 1 min.

Regards,

Aditya

[marcus_sommer]

The timeouts control the flag if a RAM part is reserved or free. There are several settings which have an impact how long an app is kept as reserved. Beside the mentioned ones probably also the document-settings.

[Aditya_Chitale]

Thanks @marcus_sommer for the reply. do you have any article where all this is well documented to that I can do some research ? any qlik page ? or other website ?

Regards,

Aditya

[PrashantSangle]

so according to this, evenif if reduce the time-out then it will revert to standard engine cache timeout.

Regards,

Prashant sangle

[marcus_sommer]

Unfortunately no. For QlikView I would know various ways - especially opening the n xml-configuration-files with an editor and CTRL + F to search and jump fast between the possibilities (most one have a small documentation what they are controlling) which are not all available within the QMC. If you are going such way make sure that you have BACKUP's from the files before manipulating them.