What the white screen of death means: Difference between revisions From Online Manual

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==Source of the Problem==
==Explanation of the Causes of the White Screen==
 
The issue appears to be that when a page is loaded, and the script tries to load one (or more) additional files to perform sub-tasks, the system runs out of allocated memory.
The issue appears to be that when a page is loaded, and the script tries to load one (or more) additional files to perform sub-tasks, the system runs out of allocated memory.


This happens most often on a shared host on an "oversold" siteYour host does not explicitly limit the memory, bandwidth, or disk space you can useBut once your shared server starts to get full, those resources will have to be shared by a number of "unlimited" accounts.  At this point, the host will have to apply "hidden" limits to the accounts to keep the accounts from overloading the server.  You will start running into memory, disk space, or bandwidth problems, or even have your forum shut down -- temporarily or permanently. Even though you are, therefore, meant to have been offered an "unlimited" service, you have not.
The reason this is happening is because those of you encountering this issue are very likely running your site on an overselling host.  This means that the host you chose sells sites with "unlimited" stuff, such as bandwidth, or disk space.  The truth is that nobody could actually afford to sell "unlimited" everything (or anything).  Hosts need to pay for expenses and make money.  The host that you chose may ''advertise'' "unlimited", but in reality, they have severely limited your account, because they put far too many "unlimited" accounts on the same physical, or virtual, machineThey then apply "hidden" limits, and shut your forum down, when your usage exceeds these limits. Even though you are, therefore, meant to have been offered an "unlimited" service, you have not.


It is important to realize that there is a limit to how much memory a given script can access, and that every host has to have limits like this. The difference is that some hosts let you know in advance what your limits are going to be, and will be able to discuss how you can get more resources if you need them.  An oversold host cannot do this, because the limits are variable.  The limits are related to how many accounts they place on the same server, how much disk, memory, CPU or bandwidth those accounts use.
It is important to realize that there is a limit to how much memory a given script can access, and that every host has a limit like this. A ''real'' host, however, has a reasonable amount, and will not put far too many accounts on a single server such that they overuse the available resources, and a ''real'' host will discuss how much you require if you truly need to exceed that amount.


In some cases, the host has set this limit very low.  So low, in fact, that the package manager cannot load Subs-Post.php to process the BBC tags in the readme file of a mod.  If that step is skipped, the script chokes when it tries to load Subs-Package.php, to actually do the install.  Processing stops before the package can be checked or installed, and the HTML document does not get created correctly.
In your case, the host has set this limit low.  So low, in fact, that the package manager cannot load Subs-Post.php to process the BBC tags in the readme file of the mod.  If that inclusion is bypassed, the script next chokes on the loading of Subs-Package.php, which cannot be bypassed because that file contains the instructions needed to process the Mod package.


==How to Solve the Problem==
==How to Solve the Problem==
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===Increase memory allocation externally===
===Increase memory allocation externally===
You can try and use a .htaccess file to overwrite the memory limit, but if the server controls it (which is probably the case, since SMF tries to set it high enough using '''ini_set''' when installing a mod package), than it probably won't work, and you are stuck with the server php memory limit.   
You can try and use a .htaccess file to overwrite the memory limit, but if the server controls it (which is probably the case, since SMF, tries to set it high enough using '''ini_set''' when installing a mod package), than it probably won't work, and you are stuck with the server php memory limit.   
Using  phpinfo() should also tell you if PHP runs in CGI mode or as an Apache module (mod_php).  If CGI mode htaccess won't work, if Apache module, use htaccess to set the php memory limit:
Using  phpinfo() should also tell you if PHP runs in CGI mode or as an Apache module (mod_php).  If CGI mode htaccess won't work, if Apache module, use htaccess to set the php memory limit:



Revision as of 20:27, 30 April 2014

Explanation of the Causes of the White Screen

The issue appears to be that when a page is loaded, and the script tries to load one (or more) additional files to perform sub-tasks, the system runs out of allocated memory.

The reason this is happening is because those of you encountering this issue are very likely running your site on an overselling host. This means that the host you chose sells sites with "unlimited" stuff, such as bandwidth, or disk space. The truth is that nobody could actually afford to sell "unlimited" everything (or anything). Hosts need to pay for expenses and make money. The host that you chose may advertise "unlimited", but in reality, they have severely limited your account, because they put far too many "unlimited" accounts on the same physical, or virtual, machine. They then apply "hidden" limits, and shut your forum down, when your usage exceeds these limits. Even though you are, therefore, meant to have been offered an "unlimited" service, you have not.

It is important to realize that there is a limit to how much memory a given script can access, and that every host has a limit like this. A real host, however, has a reasonable amount, and will not put far too many accounts on a single server such that they overuse the available resources, and a real host will discuss how much you require if you truly need to exceed that amount.

In your case, the host has set this limit low. So low, in fact, that the package manager cannot load Subs-Post.php to process the BBC tags in the readme file of the mod. If that inclusion is bypassed, the script next chokes on the loading of Subs-Package.php, which cannot be bypassed because that file contains the instructions needed to process the Mod package.

How to Solve the Problem

You now have three choices:

  1. Ask your host to increase your available memory.
  2. Switch to a non-overselling host. There are a large number of those hosts listed in our Hosts and Hosting boards
  3. See below for options that you can try (none are guaranteed to work) if you want to stay on your current host.

These hosts may be slightly more expensive than the one that you originally chose, but, as is often the case, you do get what you pay for.

Increase memory allocation externally

You can try and use a .htaccess file to overwrite the memory limit, but if the server controls it (which is probably the case, since SMF, tries to set it high enough using ini_set when installing a mod package), than it probably won't work, and you are stuck with the server php memory limit. Using phpinfo() should also tell you if PHP runs in CGI mode or as an Apache module (mod_php). If CGI mode htaccess won't work, if Apache module, use htaccess to set the php memory limit:

<?php phpinfo(); ?>
  • In .htaccess, you can try to add the following:
php_value memory_limit 64M
  • If you add this and get a 500 Internal Server Error, then your host is running PHP in CGI Mode, and you will have to increase the memory_limit in the php.ini file.
memory_limit = 64M

If you are not allowed to have a custom php.ini file, you will have to ask your host to do this.

Increase memory allocation in the file(s)

You can try to increase the memory allocation in the files and functions, directly.

  • In /Sources/Class-Package.php, find:

	// If we're using this try to get some more memory.
		@ini_set('memory_limit', '32M');

  • Replace with

	// If we're using this try to get some more memory.
		@ini_set('memory_limit', '128M');

  • in /Sources/Admin.php, find

// Get one of the admin information files from Simple Machines.
function DisplayAdminFile()
{
	global $context, $modSettings, $smcFunc;

	@ini_set('memory_limit', '32M');

  • Replace with

// Get one of the admin information files from Simple Machines.
function DisplayAdminFile()
{
	global $context, $modSettings, $smcFunc;

	@ini_set('memory_limit', '128M');



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