Use the search and browse feature to view Kepware's repository of more than 500 Knowledge Base articles. Narrow your results or type your query into the search field below.

Search Solutions Results By: View All Solutions

Kepware Knowledge Base: Solution


Static and Dynamic Tags


Last Update: 11/12/2018

Static Tags
Static Tags are tags that are created by the user in the server. They can be used to give meaning to a device address, to assign a specific data type to the tag, or to scale the raw value of a tag to a different engineering value. The client application can browse the server for Static Tags. Please note the following:

  • Unless the data type is specified, the default data type for that address location will be used. For more information on the default data type, refer to the "Address Descriptions" topic in the driver's product manual.

  • Most OPC clients allow users to specify the data type as part of the request when registering a link for a specific data item. The data type specified by the OPC client is used if it is supported by the communications driver. The @[Data Type] modifier can be useful when ensuring that a communications driver interprets a piece of data exactly as needed.

  • Non-OPC clients can override the update rate on a per-tag basis by appending @[Update Rate].

  • The exception is when using Dynamic Tags with a client driver, such as the OPC DA Client and OPC UA Client, which cannot pass a data type override with the dynamic tag request. In client drivers, the data type is unknown to the local server until that point is read, when it is assigned the reported data type in the local instance. Use a static tag defined in the local server project with the named data type in the target server for the data types to match or the data type reported by the target server is used.

Dynamic Tags
Dynamic Tags are tags that the server creates in the project on behalf of the client application's request for a device address, rather than a Static Tag that represents that address. Users should note the following:

  • Dynamic Tags can only be added at the device level. For example, users could not create a sub-group X in a device and then add an item in the client called "Channel_1.Device_1.X.R0"

Differences in Performance
Using one tag over another does not impact the performance of the project. The benefits and detriments balance out as well. With Static Tags, users can specify that clients cannot write to a tag; however, two tag databases must be maintained. With Dynamic Tags, users do not need to maintain two tag databases; however, there is no way to ensure that multiple clients request the items in the same fashion.


Note:
Users can override a static or dynamic tag update in non-OPC clients by appending the Update Rate to the item request. This value is in milliseconds. For example, "Channel_1.Device_1.R0@1000". Users can also override this by setting the Update Rate in the alias. To do so, click Edit | Alias Map in the server.

Related Products
KEPServerEX