Smart OPC XML Server provides two basic data access modules - Smart OPC XML Data Access and Smart OPC XML Historical Data Access. Smart OPC XML HDA Module is one of the basic parts of the entire Smart OPC XML Server. Configuration of the Smart OPC XML HDA module is in XML configuration file situated in <InstallDir>\Config folder.

Common Configuration Attributes

Smart OPC XML HDA Module provides an API for developing new OPC XML Historical Data Access plugins. So there are configuration parameters which are common for the module and all of this type plugins. Of course they are not mandatory and developer may override the functionality and thus to bypass them.

[LoggerName]

Provides the NLog logger name. If empty or omitted null logger will be used instead.

[MaxItemsPerHdaReadAtTime]

Maximum available items to read at once via HdaReadAtTime. 0 means no restriction.

[MaxItemsPerHdaReadProcessed]

Maximum available items to read at once via HdaReadProcessed. 0 means no restriction.

[MaxItemsPerHdaReadRaw]

Maximum available items to read at once via HdaReadRaw. 0 means no restriction.

[HdaPerformanceCountersEstimationInterval]

Interval in milliseconds of estimating HDA performance counters. Value cannot be lower than 1000ms.

[MaxHdaReadRawAfterSnapshot]

Max allowed HdaReadRaw requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaReadProcessedAfterSnapshot]

Max allowed HdaReadProcessed requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaReadAtTimeAfterSnapshot]

Max allowed HdaReadAtTime requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaGetAggregatesAfterSnapshot]

Max allowed HdaGetAggregates requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaGetStatusAfterSnapshot]

Max allowed HdaGetStatus requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaBrowseAfterSnapshot]

Max allowed HdaBrowse requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). 0 means no limit. E_REJECTED is thrown if the limit is reached.

[MaxHdaRequestsAfterSnapshot]

Max allowed requests since last counters snapshot (i.e. max number of requests are per specified performance counters estimation interval). Must be consistent with other requests type limitations. 0 means no limit. E_REJECTED is thrown if the limit is reached.

[DebugTraceFirstChanceExceptions]

If you set "DebugTraceFirstChanceExceptions" to "true", then an event handler will be attached to the application domain first chance exceptions handler and all exceptions will be traced to the log.

[DebugTraceUnhandledExceptions]

If you set "DebugTraceUnhandledExceptions" to "true", then an event handler will be attached to the application domain unhandled exceptions handler and all unhandled exceptions will be traced to the log. Also in the log will be traced if the exception is terminating or not.

Remark: Be careful when use "DebugTraceFirstChanceExceptions" and "DebugTraceUnhandledExceptions" options, the log files can grow dramatically if you leave them turned on. Use only for debugging purposes.

Configuration Attributes

Configuration attributes of the Smart OPC XML HDA Module are located in <InstallDir>\Config\Smart.OpcXml.HdaServer.Configuration.xml file. Common configuration parameters described above are entirely valid for the OPC XML HDA module. Further will be discussed how to configure which plugins to be loaded by this module at startup.

Loading Plugins

Describing available plugins to the Smart OPC XML HDA Module and which of them to load at startup is made through "<InstallDir>\Config\Smart.OpcXml.HdServer.Configuration.xml" configuration file.

Example:

   <Plugin AssemblyPath="|\Plugins\OpcHda\Bin\Smart.OpcXml.Plugins.Hda.OpcHda.dll" Enabled="true" /> 
   <Plugin AssemblyPath="|\Plugins\HdaGateway\Bin\Smart.OpcXml.Plugins.Hda.HdaGateway.dll" Enabled="true" /> 
   <Plugin AssemblyPath="|\Plugins\HdaVirtualize\Bin\Smart.OpcXml.Plugins.Hda.HdaVirtualize.dll" Enabled="true" />

To configure a plugin to be loaded you need to specify the AssemblyPath of the base plugin DLL, and to set property Enabled="true" if you want to load it on server startup. A "|" character in the beginning means that the plugin location is relative from the root installation path (e.g. "*"). You can omit the "*|" character, but then you must specify the absolute path to the plugin assembly to be loaded. The recommended location where to place your plugins is "\Plugins" folder. The default plugins wich are shipped with the distribution package are placed in the "\Plugins" folder, otherwise they won't work. Usually plugins use common server libraries located in "\Lib" folder. If you write your own plugin and want to put somewhere else than "\Plugins" you should write your own assembly resolve function in order to find and load required assemblies.

By default Smart OPC XML Server does not load any OPC XML HDA plugins at startup. Delivered plugins by the installation are commented in the configuration file (OpcHda, HdaGateway and HdaVirtualize).

Plugins

The Smart OPC XML HDA Module provides an API for creating plugins which can be loaded by it. Smart OPC XML Server comes with several preloaded OPC XML HDA plugins:

  • HDA Gateway Plugin - Provides ability for cascade-linking of OPC XML HDA Servers;

  • OPC HDA Plugin - Provides ability to inerop with classic OPC Historical Data Access Servers;

  • HDA Virtualize Plugin - Provides ability to expose virtual items in the server's address spaces, which values are delivered by making some calculations described in C# scripts.

Common Plugin's Configuration Attributes

As mentioned above the Smart OPC XML HDA Module provides and API for developing new OPC XML Historical Data Access plugins. So there are configuration parameters which are common for all of this type plugins. Of course they are not mandatory and developer may override the functionality and thus to bypass them. We must mention that Common Configuration Attributes of Smart OPC XML HDA Module are also valid here. We will describe here additional configuration attributes only.

[SupportHdaReadRaw]

Indicating whether plugin supports HdaReadRaw action:

  • true - allow browse actions;

  • false - deny browse actions;

[SupportHdaReadProcessed]

Indicating whether plugin supports HdaReadProcessed action.

  • true - allow get properties actions;

  • false - deny get properties actions;

[SupportHdaReadAtTime]

Indicating whether plugin supports HdaReadAtTime action.

  • true - allow read actions;

  • false - deny read actions;

[SupportHdaGetAggregates]

Indicating whether plugin supports HdaGetAggregates action.

  • true - allow write actions;

  • false - deny write actions;

[SupportHdaGetStatus]

Indicating whether plugin supports HdaGetStatus action.

  • true - allow subscribe actions;

  • false - deny subscribe actions;

[SupportHdaBrowse]

Indicating whether plugin supports HdaBrowse action.

  • true - allow get status actions;

  • false - deny get status actions;

[Alias]

Plugin module alias. Each plugin loaded by the Smart OPC XML HDA Module must have unique alias name which is used for prefixing address space elements ItemPath and ItemName respectively.

[PathSeparator]

Plugin module address space path separator used for the items.

[OriginalPathSeparator]

This is the path separator used by the classic OPC HDA server where the plugin is connected to. This separator will be replaced by address space translation mechanism with the plugin module address space path separator.