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Glossary
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.. glossary::

    available
        To determine if the subsystem is available, currently TMC calls the state() method on the Tango device proxy to check the device's current state.
        This is a network operation and will fail if the device is unreachable. TMC SubarrayNode reports the availability of the attribute - :term:`isSubarrayAvailable`
    
    isSubarrayAvailable
        Each TMC sub-array node has an availability attribute 'isSubarrayAvailable'. This attribute can be subscribed by client to read the availability status of the sub-array. The sub-array is said to be available only if all the critical systems it controls are available (SDP and CSP ,MCCS sub-array devices).
        TMC sub-array node Availability attribute is 'true' only if all below conditions are satisfied :

        #. SDP sub-array leaf node is reachable (through the reading State of device), and reports its availability attribute as true on isSubsystemAvailable.
        #. CSP sub-array leaf node is reachable (through the reading State of device), and reports its availability attribute as true on isSubsystemAvailable.
        #. Third condition is based on Telescope, whether it is **Low** or **Mid**:

            - **For Low**: MCCS sub-array leaf node is reachable (through the reading State of device)
            - **For Mid**: Dish subarray leaf node is reachable (through the reading State of device)

    TRL
        It stands for Tango Resource Locator. Check `ADR-9 <https://confluence.skatelescope.org/display/SWSI/ADR-9+Update+naming+conventions+for+TANGO+Devices+and+Servers>`_ for more details.