IDAS autonomous startup

Normally, the AVEVA Historian Configuration Service starts an IDAS. However, a remote IDAS that is enabled for store-and-forward can be configured to start independently of the Historian. Autonomous startup is useful when the Historian is unavailable due to a network failure or when the Historian is not running when the remote IDAS computer starts. Using autonomous startup, the IDAS starts caching store-and-forward data without waiting for a command from the Historian.

For an IDAS to autonomously start, it must be configured to acquire data from at least one data source. During the configuration process, the IDAS must be connected to the Historian to ensure that the configuration file is created on the local IDAS computer. An autonomous startup requires an existing local IDAS configuration file on the IDAS computer, so that it has all of the information it needs to begin acquiring data. For more information, see IDAS configuration.

When an IDAS starts, it attempts to load the configuration information from the local configuration file. If it is able to do so, the IDAS uses that information to connect to its data sources and start acquiring data. As soon as the internal IDAS data buffers are full, the IDAS switches to store-and-forward mode and stores data to the local hard drive.

If there is more than one autonomous configuration file on the IDAS computer (for example, if you deleted an IDAS on a node while it was disconnected and then added one again), only the newest file is used. A warning is logged on the IDAS computer.

If the local configuration information cannot be loaded, the IDAS remains in an idle state until contacted by the Historian. If the IDAS is not contacted by the Historian within the default start time-out of 60 seconds, the IDAS shuts down. Note that the IDAS startup time-out is different than the time-out used by the IDAS during autonomous startup. Information on changing the default IDAS startup time-out is provided in a TechNote, which is available from technical support.

When the Historian becomes available, data transmission from the IDAS will be restored. For more information, see IDAS store-and-forward capability.