[Qgis-user] Qgis crashes while loading WMTS layers

[Bo Victor Thomsen]

Hi Patrick -

Swap space is an internal component the underlying operating system (OS) 
uses for handling memory request that exceeds the ram resources of the 
computer. A normal user program like QGIS has no "knowledge" about this 
facility and can't directly manipulate the swap system.

As Jonathan describes, "swap" space for for other program is temporary 
file storage, usually placed in a specific directory (in windows 
designated by the environment variable %TEMP%). QGIS uses this directory 
too.

A QGIS crash can be caused by running out of memory resources and/or 
temp file storage. However, that is result of a bad setup of your 
operating system, which can limit how much swap space, that can be 
allocated to memory hungry programs and the size of hard-disk used for 
swap space and/or temp storage

So what to do:

 1. Check memory consumption when using QGIS. Is it really using all the
    ram - memory and starting to swap ?
 2. Check the setup of the swap space parameters. It it using a
    hard-disk which is running out of storage space.
 3. Check the setup of the temp storage parameters. It it using a
    hard-disk which  is running out of storage space ? Are the user
    allowed to allocate enough storage?

(I can't be more specific not knowing the operating system you use)

If the above checks out OK and you still have issues with QGIS crashing..

The shift from QGIS 2.x to QGIS 3.x meant a complete change of the 
underlying graphics subsystem QT from ver 4.x to ver. 5.x (and a huge 
amount of other changes).

One or more of those changes  might cause a failure as you described. 
However, you have to check the above and then write an error issue 
(https://github.com/qgis/QGIS/issues) where you describe error messages, 
your specific setup like operating system and version, QGIS version and 
- if possible - test-data and project to replicate the issue.

-- 
Med venlig hilsen / Kind regards

Bo Victor Thomsen







Den 26-01-2020 kl. 13:19 skrev Patrick Dunford:
> Good day to all.
>
> Not so long ago I wrote a post about issues handling large numbers of 
> raster files. This results from what appears to be an architectural 
> design limitation of Qgis in that it only has enough resources 
> available for a certain (unknown) number of raster layers and does not 
> have any effective system for dealing with the exhaustion of these 
> resources.
>
> I also noted that the software does not appear to have the ability to 
> use the swap (virtual memory) resources within a system to deal with 
> the apparent exhaustion of resources, as other software would. For 
> example, Gimp which I use for graphical editing is able to handle 
> certain projects using a swap space of 200 GB, which consists of 32 GB 
> of physical RAM and the rest in SSD. It is not unusual with some of 
> these graphics projects to have 100 GB or more of swap space in use, 
> without crashing the system. (This being possible since Gimp 2.10 with 
> its ability to write files of more than 4 GB)
>
> Whilst it is possible to manage the number of layers with file based 
> rasters, this cannot be done with a WMTS server because there is no 
> way I am aware of to manage the number of layers that can be 
> downloaded from the server.
>
> Version 2.18 and earlier almost never crashed with excess layers, 
> usually all that would happen is a layer would be displayed with 
> invalid data. However, crashes have become the norm with 3.x versions 
> of software.
>
> It seems to me there is a big architectural problem in the software 
> with its inability to utilise the full resources of the system in 
> order to process the number of layers that a WMTS server is capable of 
> issuing.
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20200127/b4c94c46/attachment.html>