Hello there,
Total newbie here, apologies for any silly questions I might ask... (and the very long post!).
I've been using Limesurvey for the past year without issues and love it. Now I'm working on a major survey and need it out soon. However, since Thursday pages have been going blank, seemingly randomly. The issue first started after having worked on a survey for a couple of hours, then suddenly the next group page was just blank. Reloaded page, nothing. Restarted Chrome, nothing. Cleared cache, could then log in, go to the survey list page, but clicking on any survey would just bring up a blank page - and after that all pages were blank including the admin login page. Changed to Firefox and the scenario repeated. Changed to IE and the scenario repeated. Tried to go to an activated survey to fill it in and it was a blank page as well.
Contacted the server host (one.com) where they reported no issues and no updates had been implemented. Trawled the Limesurvey forums with no luck (found this which seems to be the same issue but no resolution: www.limesurvey.org/en/forum/design-issue...after-a-while#122389 ). Tried to log in again several hours later and everything worked! For a couple of hours, then everything went blank again. Next day, same thing: could log in and work for 1½ hours, then everything went blank. No errors came up. This morning things were working again. Tested the survey in the Limesurvey demo and it works. Again after about 1½-2 hours working on the survey, it's now blank again. I can't risk deploying a survey if it goes blank randomly so hope you can help?

Tried a couple of things yesterday, but issue there again today:
1) Added to .htaccess file in /limesurvey:
# Set some options.
#Options -Indexes
#Options +FollowSymLinks

2) Changed the limesurvey config-defaults.php memory limit from 32M to 128M

Limesurvey: Version 2.05+ Build 141020
PHP version 5.6.12
Server: Linux web20 3.10.54-20140916-1425-05f4076 #1 SMP Tue Sep 16 14:26:20 UTC 2014 x86_64
PHP memory_limit: 128M (thought that might be the issue, but I get no memory errors and from what I can see this should be enough? Can't upgrade as it's on one.com!)

I have 2 open surveys, 5 unactivated surveys and 11 expired surveys. I thought cleaning up would be a good idea so I deleted a survey that was no longer needed on the same day that the issue started - can deleting a survey mess up the system like this?

The survey in question is quite large (?), 58 groups, 113 questions but with lots of relevance equations, so respondents are split into several groups and only answer a smaller subset of questions. Questions are a mix of all types. No embedded files or anything out of the ordinary.

I set debug to 2 this morning when things were working. No errors have come up, the page just went blank.

Any help or ideas would be greatly appreciated! Thanks

My first guess would be that the problem is the size of the survey. 58 groups with 113 questions and lots of relevance equations could lead to some problems.

Within those questions, how many are multiple choice questions? How long are the lists of items for these multiple choice questions? I am asking, because with long multiple choice questions that repeat you can easily reach the limit of the database which is usually slight above 1000 columns, depending of the installation you are using.

There are quite a lot of array questions with up to 11 x 11 answer options. Downloading completed responses to a previous test gave 504 answer columns + 162 time columns. Ah, hadn't actually thought about the timings... Might it help to deactivate the timing? Only really needed it for the test, but can disable in the main survey. Or do those columns not count?

The array questions are not such a big problem, because the answers to each subquestion are stored in the same column (e.g. only the answer code is stores). But if you have a lot of subquestions, this of course adds up, just like the multiple choice questions (each answer option is one column stating if the the box was ticked or not).

Now the timings could be a problem, because per question, there will be an extra column. I am not sure, but I think they are stored in the same database table (but I am not expert on this).

Don't think I have any multiple choice questions at all. Mostly arrays, a few radio buttons and a couple of open text boxes.

Once I have access again (don't understand how it usually works after a few hours again?), I'll disable the timings.

Just chatted to one.com and technicians say there is no column limit on the database.

Thanks for your quick replies! Any other ideas welcome. Will report back if disabling timings solves this.

Limesurvey as well has no column limit. However, Mysql, depending on the engine HAS a limit. That is explained in the manual. So while Limesurvey (or One.com) does not put you a limit, the database does. It is not infinite...

But just to make this clear: I am not saying that you are running into this limit. It is just a possible cause of problems.

If it works again after a few hours, this sounds strange to me and rather like a problema of One.com than Limesurvey.

I don't know One.com, but it sounds like a shared hoster to me, right?

2) Changed the limesurvey config-defaults.php memory limit from 32M to 128M

Limesurvey: Version 2.05+ Build 141020
PHP version 5.6.12
Server: Linux web20 3.10.54-20140916-1425-05f4076 #1 SMP Tue Sep 16 14:26:20 UTC 2014 x86_64
PHP memory_limit: 128M (thought that might be the issue, but I get no memory errors and from what I can see this should be enough? Can't upgrade as it's on one.com!)

The change in the Limesurvey Defaults doesn't help much, when the host limits you. However, you posted that the php memory limit is 128M, this should usually be enough for most things. But I have my doubts that those 128M are what One.com allows you to use for your processes. This would be quite a lot for a shared hosting environment.

Yeah, I know it's limited, just annoying that you can't get a proper answer from one.com... And yes, it is a shared hoster. Not sure that is the issue though as I should be under the limit... Not sure where to find the limit info but I'm sure it's here somewhere: one-docs.com/mysql ?

Getting the PHP info from Limesurvey and from one.com both say 128M. Not sure how to actually work out how much I can use?

Just managed to log in again now and change timings. So, this time I was 'blank-paged' for about 1½ hours. Will see for how long it will work...

Turned out it would only work for about 15 min. so I'm now blank-paged again.

Could it be a time-out issue? It has the 'Waiting for mysite.com...' for a while, then blanks. If yes, what can be done?

I am not quite sure, because this sounds clearly like a hosting problem.

Do you have a local test environment with Limesurvey? Export your survey and import it there and see what happens.

if you want, you can send me the survey and I try it here on my server to see what happens. But if the whole installation is affected (can't login, etc.), then I guess it is not a normal memory problem or a problem with the table columns, but rather some measure on your hosting companies end.

By the way: don't send the survey here, if you want/can share it. Send me a private message.

Thanks for offering. I do have Limesurvey on Xampp installed and just imported the survey to there. So far, no problem - but then the issue usually only starts after 1½ hours, so I guess I know what I'll be doing tonight! If that works, I guess it is a hosting issue...