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Background information and general remark
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Cassandra_ is the current (2018) archiving solution used at KARA. There is a `JavaScript-Object-Notation`_-API available, that can be accessed from within the IBPT-LAN (CN, VPN or las-bernhard.anka.kit.edu).

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Usage with different hosts or ports
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In case you want to run this scripts or library from a place where the host or port does not fit the presets, you need to provide them as environment variables.
For example if you want to run your script ``cassandra_download.py`` and you forwarded ``ankacomm`` via SSH to the port 9999,
you can then call your script in bash like::

   CASSANDRA_HOST=localhost; CASSANDRA_PORT=9999 python3 cassandra_download.py


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Terminology
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EPICS — KARA's currently used control system, in which e. g. CLIC-damping wiggler is integrated into. This system feeds its values to the Cassandra-db. More information on EPICS can be found in the working group presentation done by Walter Werner at CS or in the ANKA-Confluence, as well as the `official EPICS website`_

PV — EPICS-Variable, (Process variable) are  the variables you can ask EPICS or Cassandra-db for. They look something like `A:SR:S1:What:Not:01`. A list of oftenly used ones is also included in the :class:`Pvs`.

CSS — The Control System Studio is the graphical user interface used for the EPICS control system. It can export data which can be imported using function of the :mod:`css_read` module.

.. _Cassandra: https://cassandra.apache.org/
.. _`official EPICS website`: https://www.aps.anl.gov/epics/


JSON-Files
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./\*json are files that are requested via the webfront end of the Cassandra-db. They are formated in the `JavaScript-Object-Notation`_
The URI scheme is described in the `ANKA-Confluence`_.

.. _`JavaScript-Object-Notation`: https://de.wikipedia.org/wiki/JSON
.. _`ANKA-Confluence`: https://ankawiki.anka.kit.edu/display/MACHINE/Cassandra+Web+Readout