Refresh

Associated with: OPC UA Subscriptions and OPC UA Points

Security permission required to access this pick action: Retrieve Data

Geo SCADA Expert typically reads items for data on a scheduled basis. If required, you can use the Refresh pick action to read items on demand. Select the Refresh pick action to display the following window and request a current data update of the point or points that are associated with a particular OPC UA Subscription.

Select the pick action on a specific point to refresh the data for just that point. Select the pick action on an OPC UA Subscription item to refresh the data of the points on that subscription.

The pick action is only available on OPC UA Subscriptions and Points that are 'live' and in communication with an OPC UA server to which to which the Subscription relates.

• Source—Use to select the source of the data, the options are:
  • Cache—Use to select the Cache as the source of data. Access to the Cache data is expected to be 'fast' and should contain the latest value of the data (this depends on the point's sampling interval (update rate) and deadband optimizations) as well as the quality and timestamp. The timestamp indicates the time that the value and quality were obtained by the device (if this is available) or the time that the OPC UA server updated or validated the value and quality in its Cache.
  • Device—Use to select the device as the source of data. Accessing data from the device is usually slower than from the Cache and is expected to be used primarily for diagnostics or for particularly critical operations.
  • Either Cache or Device—Select this option for the OPC UA server to determine whether the data is obtained from the Cache or the Device. If you select this option you need to specify a Maximum Age for the data (see below).
• Maximum Age—Specify the Maximum Age interval in milliseconds. Enter the required interval in the OPC Time Format. You can enter the value directly in the field, or use the Interval window (accessed via the field's browse button) to specify the required value.

  The OPC UA server checks the timestamp on each item. Where the data for an item has been updated within the Maximum Age interval the data is obtained from the cache. If the timestamp is not within the Maximum Age interval the data is obtained from the device.