.. _ioc_guidelines:

IOC Guidelines
##############


The EPICS IOCs used for control and monitoring in the NUSTAR DCS sub-systems should follow some general guidelines.

Guidelines
==========

Standard records
----------------

The IOC database should contain a few standardised records

* `ioc:status` record
  The status record provides a standard record to indicate that a certain IOC is active::

      record(bi, "$(PREFIX):ioc:status") {
        field(DESC, "NUSTAR DCS status")
        field(ZNAM, "Not OK")
        field(ONAM, "OK")
        field(VAL, "1")
        field(PINI, "YES")
      }

* `ioc:error` record
  The error record provides a standard record for error/state messages. Other records in the IOC should use this record to communicate error and state conditions (29 characters maximum)::

      record(state, "$(PREFIX):ioc:error") {
        field(DESC, "NUSTAR DCS error message")
        field(VAL, "Undefined")
        field(PINI, "YES")
      }

* `ioc:state` record
  The state record is used in sub-system overview IOCs and provides a standard record that shows the state of the sub-system state machine (see also :ref:`nustar_dcs_sub_system_state_machine`)::

      record(state, "$(PREFIX):ioc:state") {
        field(DESC, "NUSTAR DCS state")
        field(VAL, "Undefined")
        field(PINI, "YES")
      }

IOC Startup
-----------

* IOC installed on single-purpose PC (only for one or more IOCs):
    * IOC should start automatically at boot-up. This can be realised e.g. using an entry in the crontab
    * IOC should be started in the background using `procServ`, on standard port 2222
* IOC installed on a multi-purpose PC (also other functionality):
    * IOC should be started from within a screen session

IOC Reboot
----------

After a reboot of the IOC, the device should be in a safe and usable state. It should be fully controllable by only using Process Variables defined in the IOC. 

If possible, the IOC should make use of the `bumpless reboot` feature offered via the `autosave` module. This allows for automatic restoration of the previously set values.