Added to Horde_Core 2.13.0.

Slightly more serious than originally believed, since excessive large 
import data could cause unexpected session failure.

Changes have been made in Git (master):

commit 4a0538ac6db84ac68d00ee55fd6e53905ac59534
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Thu Jul 24 23:03:36 2014 -0600

     [mms] Horde_Data now stores temporary data using Horde_Vfs to 
ensure data persists and that it doesn't overload session storage 
(Request #11335)

     Horde_Core_HashTable_PersistentSession has been added to provide a
     solution to allow for "persistent" session storage. This means that the
     data is guaranteed to exist for the life of the session (but no more).

     This fixes the potential of destroying a session by importing too much
     data (e.g. in Turba Import screen).

  framework/Core/lib/Horde/Core/Data/Storage.php     |   42 ++++++--
  .../lib/Horde/Core/HashTable/PersistentSession.php |  111 
++++++++++++++++++++
  framework/Core/package.xml                         |   11 ++-
  3 files changed, 154 insertions(+), 10 deletions(-)

http://github.com/horde/horde/commit/4a0538ac6db84ac68d00ee55fd6e53905ac59534

Yes, this is a limitation of the current Horde_Data package.

I previously abstracted out the storage to a separate driver 
(Horde_Data_Storage), but Horde_Core currently only implements session 
storage (Horde_Core_Data_Storage).  A VFS based driver would need to 
be written (we can't use Horde_Cache since there is no guarantee of 
data permanence).

When I try to use Horde_Data_CSV with large CSV files my session is 
"destroyed".

AFAIK this is because the whole uploaded file is stored in session and 
somehow when I am using Memcache as the session handler and not File 
this bug occurs.

PS: If someone point me to the right direction and I will be happy to 
contribute with a patch.