This is a server setting issue. Your PHP configuration must be able to accept a number of POSTed values that high.

I have googled this a bit but don't know much about PHP server setup.
Is adding the following what you are suggesting
post_max_size = 5001
max_input_vars = 5001
If so, it doesn't seem to fix the problem.

Well, it is not a bug of LimeSurvey. Try to check the available memory, maybe it is too low.

Hi Carsten,
Isn't unintended behavior without explanation is a bug? If it comes with some explanation, even as little as "bad configuration", then maybe not, but without any explanation, it's a bug. Or how do you define bug?

"free" at the console gives me
total used free shared buffers cached
Mem: 1024000 500952 523048 0 0 408616
-/+ buffers/cache: 92336 931664
Swap: 0 0 0

Is that too low?

I am now using the following:
memory_limit = 128M
post_max_size = 64M
max_execution_time = 500
max_input_time = 500
Still having the same problem. What settings should I use?

Hi ttenbergen. I'll have a look at this. The root of the problem is that admins can't edit each others participants, right?

That's the root, yes. For me. It goes a step further in its bugginess, though, because it looks like you are changing e.g. emails or attributes, but the edits don't stick.

But fundamentally, if you can't assign rights for more than 500 at a time that will still be a bug for anyone trying to use user rights on CPDB.

Thanks for having a look Olle!

Thanks for your info. I'll try to fix the root problem first.

If you make users superadmin AND share the CPDB participants with everyone, then everyone can edit.

You are correct. Yet right now, sharing all participants is painful because I can only do it 500 at a time. We have ~1100 so I need to do it in three steps for each user. And every few weeks I have to do it again because new participants are added that non-owning users don't have rights to. So, yes, I have an awkward work-around, but it keeps leading to support calls.
Doesn't help that you can't share a participant with yourself, even as a super user, so I can't even give instructions to my superusers how to do this themselves.

We will change it for 2.50 so superadmin can see everyones participants.
Superadmins should have no limitation in general.

BTW; memory_limit is a bit low - also have a look at this page

https://manual.limesurvey.org/Troubleshooting#After_submitting_a_page_with_big_number_questions.2Fanswer_options.2Fsubquestions_they_are_not_saved

Probably max_input_vars needs to be raised.

OK, there were extra variables in there that did the trick. I now use the following, and was able to share all 1150 participants in one go. Likely not all were necessary, but won't mess with that system now it works. Thanks Carsten!
memory_limit = 128M
max_value_length = 5000000
max_vars = 5000
upload_max_filesize = 64M
post_max_size = 64M
max_execution_time = 500
max_input_time = 500
max_input_vars = 5000

Suggestion: would it be worth putting a test for that into the install script?

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=17164

Fixed by letting superadmins edit participants without sharing.

2.50+ Build 160206 released