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<p>Hi Patrick -</p>
<p>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.</p>
<p>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.</p>
<p>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</p>
<p>So what to do:<br>
</p>
<ol>
<li>Check memory consumption when using QGIS. Is it really using
all the ram - memory and starting to swap ?</li>
<li>Check the setup of the swap space parameters. It it using a
hard-disk which is running out of storage space.</li>
<li>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?<br>
</li>
</ol>
<p>(I can't be more specific not knowing the operating system you
use)<br>
</p>
<p>If the above checks out OK and you still have issues with QGIS
crashing..<br>
</p>
<p>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). <br>
</p>
<p>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 (<a class="moz-txt-link-freetext" href="https://github.com/qgis/QGIS/issues">https://github.com/qgis/QGIS/issues</a>) 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. <br>
</p>
<pre class="moz-signature" cols="72">--
Med venlig hilsen / Kind regards
Bo Victor Thomsen</pre>
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<p> </p>
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<div class="moz-cite-prefix">Den 26-01-2020 kl. 13:19 skrev Patrick
Dunford:<br>
</div>
<blockquote type="cite"
cite="mid:e608e1cc-ef40-b259-9c67-177ecb1bfa8c@gmail.com">Good day
to all.
<br>
<br>
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.
<br>
<br>
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)
<br>
<br>
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.
<br>
<br>
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.
<br>
<br>
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.
<br>
<br>
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<pre class="moz-signature" cols="72">
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