Interactive jobs
=======================  

Recall the comments in :ref:`login node vs compute node`.  

An example of getting an interactive session with 1 CPU core, 2GB of memory, for 2 hours:

.. code-block:: text

    qrsh -l h_data=2G,h_rt=2:00:00


Details:

- By default, 1 CPU core is used. 

- There should be no space in between the items among the ``-l`` options. Adding spaces causes errors.

- There will some wait time, especially when requesting longer time or a larger memory size.

- When ``qrsh`` cannot be returned within a few minutes, try shorter time (e.g. 2 hours or less) and smaller memory amount, if applicable.

- The interactive session returned by ``qrsh`` is a login shell, differnt from that of a batch submission (using ``qsub``). Their differences is a common source of confusion. (A login shell is initialized differently from a non-login shell.)

- Having a long qrsh session is possible but not recommended.

    - Long qrsh session is susceptible to interruption, which may terminate the session. 
    - The wait time could be long (e.g. hours)
    - You could be “wasting” CPU time: occupying the CPUs and memory while idling.
    - If you plan to run long qrsh sessions, consider converting it to a batch submission.




More details about ``h_rt`` and ``h_data``:

.. toctree::
    :maxdepth: 1

    h_rt.rst
    h_data.rst
    ex1.rst
    ex2.rst