Timeseries Caching

In a typical APIS configuration, the real-time data collected, will be stored locally into an APIS HoneyStore timeseries database, by using an APIS Logger module.

Timeseries on a generic item in APIS

When reading timeseries data on a regular item in the Hive namespace, it is required that the item is being stored into a HoneyStore timeseries database, typically by utilizing a APIS Logger module.

Then, the horizon of the timeseries data is decided by the HistoryLength property of the corresponding item in the HoneyStore database. Typically, this HistoryLength property is specified indirectly by the Historylength_X and Historylength_Unit properties of the APIS Logger module responsible for storing the real-time item data.

Timeseries on an OpcUa client item in APIS

When reading timeseries data on an APIS OpcUa client item in the Hive namespace, the read operation may be extended to query the underlying OpcUa server of the APIS OpcUa module.

First, the read operation is handled as if it was an generic item, i.e. reading timeseries data from the corresponding item in the HoneyStore database. If the item is not stored into any local Honeystore database, or if the local storage did not return data for the complete requested time interval, the read request will be extended to the underlying OpcUa server of the APIS OpcUa module.

Hence, you can have a shorter cache of timeseries data locally, and keep a longer timeseries storage on the remote OpcUa server location. In order for this to work, the underlying OpcUa  server must implement the HistoryRead service. Of course, the APIS Hive OpcUa server implements the HistoryRead service.

Disable Timeseries Caching feature

The feature described above, is enabled by default. If you want, you can disable this feature across all items in your Hive instance.

To disable, please create the following registry key/value:

HKEY_LOCAL_MACHINE\SOFTWARE\Prediktor\Apis\<_InstanceName_>\TimeSeriesAccess\
dword:EnableExtendedReads"=00000000

If you create/modify this value, you will have to restart your Hive instance to make it take effect.