My OTRS worked just fine when suddenly system keep logging me out. After a lot of attempts, I couldn't log in, because 'session was full'. Because I couldn't find solution and this was my test OTRS on my own PC virtual machine, I re-installed Apache and OTRS (I left MYSQL as it was). Even after re-installing, I am still having the same problem.
My log:
Am using OTRS 4.0.11 on CentOS 6.[Mon Sep 14 13:16:59 2015][Notice][main::_Start] Scheduler Daemon start! PID 7062
[Mon Sep 14 13:18:54 2015][Notice][Kernel::System::User::SetPassword] User: 'root@localhost' changed password successfully!
[Mon Sep 14 13:18:54 2015][Notice][main::_AutoRestart] Config.pm changed, unsafe to continue!
Scheduler is restarting...!
[Mon Sep 14 13:18:54 2015][Notice][main::_Start] Scheduler Daemon start! PID 7068
[Mon Sep 14 13:19:11 2015][Notice][Kernel::System::Auth::DB::Auth] User: root@localhost authentication ok (Method: sha256, REMOTE_ADDR: 10.0.0.113).
[Mon Sep 14 13:19:12 2015][Notice][Kernel::System::AuthSession::DB::CheckSessionID] SessionID: 'ea8SwsASPixLZxmkmSZMZ2WLThZCbVeL' is invalid!!!
[Mon Sep 14 13:19:48 2015][Notice][Kernel::System::Auth::DB::Auth] User: root@localhost authentication ok (Method: sha256, REMOTE_ADDR: 10.0.0.113).
[Mon Sep 14 13:19:51 2015][Notice][Kernel::System::AuthSession::DB::CheckSessionID] SessionID: 'mGvAkr3ub1EAuguWBdbc3F0VSbCaJWmN' is invalid!!!
[Mon Sep 14 13:20:02 2015][Debug][main::_Status][580] Scheduler Daemon status request! PID 7068
[Mon Sep 14 13:20:02 2015][Notice][Kernel::System::GenericAgent::JobRun] Run GenericAgent Job 'send escalation notifications' from config file.
[Mon Sep 14 13:20:02 2015][Notice][Kernel::System::GenericAgent::JobRun] Run GenericAgent Job 'trigger escalation events' from config file.
[Mon Sep 14 13:25:02 2015][Debug][main::_Status][580] Scheduler Daemon status request! PID 7068
[Mon Sep 14 13:29:01 2015][Notice][Kernel::System::Auth::DB::Auth] User: root@localhost authentication ok (Method: sha256, REMOTE_ADDR: 10.0.0.113).
[Mon Sep 14 13:29:17 2015][Notice][Kernel::System::User::UserUpdate] User: 'root@localhost' updated successfully (1)!
[Mon Sep 14 13:29:17 2015][Notice][Kernel::System::User::SetPassword] User: 'root@localhost' changed password successfully!
[Mon Sep 14 13:29:37 2015][Notice][Kernel::System::AuthSession::DB::CheckSessionID] SessionID: 'EKzgGjApcXlu7GKhJ6PtZzB4AoSbUOFS' is invalid!!!